According to sources close to the situation, neither CEO Mark Pincus nor one of its principal venture shareholders, Kleiner Perkins, will be selling any shares in its upcoming initial public offering.

While big investors often divest stock in IPOs, not all do. It is a carefully watched number by investors, who are always wary of insiders who unload a lot of shares in an offering.

But such activity by the fast-growing San Francisco online gaming company will be watched carefully since Pincus has recently been painted in a number of press reports as the greedy Mr. Potter of Silicon Valley.

Among the allegations is that he runs a poisonously tough culture that tracks its employees’ output and performance via elaborate data models that require extraordinary amounts of work, along with nefarious list-making of who’s naughty and who’s not.

That big-brother behavior has reportedly included taking away high-ranking jobs and the sweet stock options that go along with them from those execs found wanting.

While there is no doubt Pincus is a hard-charging personality, his defenders note that it’s due to a belief that life at Zynga is a meritocracy and that his practices are not any more heavy-handed than those at other firms.

Indeed, Pincus has a lot of competition in the tough-guy tech CEO category from longtime legends such as Microsoft’s Bill Gates, who set the gold standard for mean, as well as Amazon’s Jeff Bezos and now Google CEO Larry Page.

Pincus does not even rate in this pantheon, which is more typical of tech companies than anyone would care to admit or, to be fair, care to care about. With big benefits, vast wealth and much latitude, many in tech don’t mind the grueling work schedules.

After all, it’s not exactly ditch-digging, now is it?

In any case, sources said the coverage has hit Zynga staff hard, as well as Pincus, who has not responded due to the IPO’s quiet period. That’s in contrast to Groupon, the daily-deals site whose own rough process was rife with highly negative stories about the company’s prospects.

While those media accounts were more aimed at the business itself and less personal, Groupon CEO Andrew Mason vociferously defended the company in a controversial letter that was then leaked and published (to me and by me!).

Pincus will doubtlessly have a lot to say to investors who ask about the company’s culture and its possible negative impact on attrition, as some stories have charged.

His decision not to sell, sources said, was inspired by Zynga investor and close friend Reid Hoffman, who has sold very little of the stock of LinkedIn, where he serves as chairman.

The action all begins next week, according to multiple reports, when Zynga takes its show on the road in preparation for an IPO that is expected to value the company at $15 to $20 billion and will take place before the new year.

It will debut under the ZNGA ticker on the Nasdaq market.

While some have been worried about Zynga’s future growth, its past performance has been a lot stronger than other Internet offerings. In the first nine months of the year, the company posted $828.9 million in revenue, double the amount from a year ago, with net income of $30.7 million.

Pincus’s holding onto shares will be seen as a plus, of course, although he has sold a large amount of stock in Zynga’s history.

According to its S-1 filing:

“From our inception in October 2007 to date, Mr. Pincus, our Chief Executive Officer, Chief Product Officer and the Chairman of our Board of Directors, has purchased an aggregate of 149,197,328 shares of our common stock. To date, Mr. Pincus has sold an aggregate of 43,629,310 shares of our common stock at prices ranging from $0.42 to $13.96.”

Pincus now holds 91.4 million of Class B shares, 16 percent of the total, as well as 20.5 million of Class C shares, 38 percent of that group. Kleiner holds 65.2 million shares, or 11.2 percent, of Class B shares.

Other big Zynga owners, who might or might not sell at the IPO, include Institutional Venture Partners, Union Square Ventures, Foundry Venture Capital and Avalon Ventures.

It used to be, many years ago, that longtime Silicon Valley tech exec Eric Schmidt could work up a very significant head of steam when talking about the thuggish monopolistic practices of Microsoft and its negative impact on the tech industry.

And, for the most part, Schmidt was dead right–Microsoft’s overwhelming power then had a malevolent impact, both directly and indirectly, on innovation and openness in the digital sector.

Thus, BoomTown is both gobsmacked and a bit in awe that Schmidt–now sitting atop the high-tech pig pile as CEO of the powerful search giant, Google–can, with a straight face, make the argument that everyone is wrong to be nervous about its deal with Yahoo to serve some of its search and text advertising, even though the pair control more than 80 percent of the search market.

Because while Google displays none of the bullying tactics of Microsoft in its glory days–think of it more like a giant that could accidentally squash all us little people with its big dumb feet–the worries about it amassing too much power are well-founded.

Along with customers, competitors and anyone who fears a concentration of power in the hands of one player, I have been a critic of the deal since it was announced in the spring as a Hail Mary play to get Yahoo out of the clutches of Microsoft.

In addition, the Justice Department has hired an outside litigator to decide whether to proceed with an antitrust investigation of the deal and possibly look into Google’s business more deeply.

And just today, comScore released new stats for search market share for August; Google’s rose once again to 63 percent, up from 61.9 percent.

Both Yahoo (YHOO) and Microsoft (MSFT)–the distant No. 2 and No. 3–lost share, logging in at 19.6 percent and 8.3 percent, respectively.

In addition, Google (GOOG) accounted for 77.4 percent of all search engine spending in the second quarter of 2008, according to Efficient Frontier.

And–oh, yes–Google-owned YouTube dominates online video rather significantly.

Translation: Scary, like that-bullying-banker-Mr. Potter-from-”It’s a Wonderful Life” scary.

Still, at a press conference yesterday– my invitation must have gotten lost in the email so I will have to rely on the quotes collected by others–Schmidt went on the offensive to defend the Yahoo deal, which is set to begin in a few weeks, in a most peculiar way.

“While we have been talking to regulators, we don’t know what their position is,” Schmidt said. “We don’t know if they think it’s a good deal or poor deal.”

But Schmidt and other Google execs–including co-founders Larry Page and Sergey Brin–said they would move forward with or without regulatory approval.

“Time is money in our business,” said Schmidt, who also noted the deal was “designed precisely to meet the terms of antitrust law in the United States.”

Well, I am not sure being within the letter of the law is quite the argument I would make. After all, one can be entirely correct–and Google does love to be mathematically accurate!–and still be completely wrong.

Yet Schmidt pressed on!

“You face a question as a large company trying to change things: How many initiatives do you want to take on that are unpopular or lead to criticism?,” he asked, pontificating as if he were fighting for better health care for the world’s poor instead of just being able to sell small text ads hawking things like Viagra and electronics.

Schmidt said the deal would have “strong user benefits” and not raise online ad prices, part of Google’s basic argument that its auction-style business model makes that impossible.

As a side note, Brin–who was, I think, being completely genuine–said Google also felt a debt to Yahoo co-founders Jerry Yang and David Filo for helping Google get started a decade ago.

(Ironically, being the search option on Yahoo’s homepage was the key way Google grew and Yahoo damaged its future prospects).

But, while the payback argument is very touching, it ignores the fact that–on its very face–the No. 1 and No. 2 search and search-ad companies should never be in business together.

That Google leadership does not seem to understand these fears is disturbing.

And with what can only be described as an oafishly arrogant style, they seem to be dismissing anyone who raises concerns as being uneducated or simply a front for Microsoft’s lobbying efforts.

“We are quite certain Microsoft is busy helping everyone get upset about things,” said Schmidt, who has long loved to slap Microsoft at any opportunity.

As if we are all in the thrall of Microsoft (whom I, for one, smack around daily for its dopey Web strategies).

Google, it seems, is in the thrall of no one.

While the deal has been voluntarily delayed by three months, the redacted agreement Yahoo released said it had 105 days from June 12 to start. That would be Sept. 25.

Under terms of the agreement, either Yahoo or Google could end the deal after 120 days from when it was struck, if it was not “commercially reasonable” for either to defend. That would be Oct. 11.

In addition, Yahoo or Google can end the deal if a court later enters an injunction.

But Google does not seem to care about a possible noisy government investigation, which it should.

While Google is in no way guilty of the kind of behavior that got Microsoft into hot water, not caring what anyone thinks was perhaps the most disastrous error of hubris that Microsoft’s Bill Gates (he is pictured on the stand here) made when the federal government came at him and took him to trial.

After a long and bruising court battle in which the judge ruled the company had violated antitrust laws, in which Gates came off very badly, Microsoft eventually settled via a consent decree to rein in some of its behaviors.

And I think we can all agree that Microsoft emerged from that encounter deeply wounded and with diminished momentum that continues to resonate today for it.

There was one thing that Schmidt said yesterday at the press conference that I do agree with: “There is a natural fear of things getting larger.”

Yes, Eric. And, naturally, more people than ever fear Google.

And while that fear has not seeped down to consumers and impacted Google’s terrific brand quite yet, it surely will, especially if Google keeps claiming that it is not all that powerful when anyone with eyes can plainly see that it is.

Just ask Microsoft.

Please see this disclosure related to me and Google.