Colleran, who has worked at Facebook longer than anyone except Mark Zuckerberg, said he did not have immediate plans post-Facebook besides taking time off and traveling.

Colleran added that he will remain involved in the industry, with advisory roles at Causes, My Basis and Buddy Media. And for good measure, “I also hope to eventually do some additional angel investing as well as potentially some consulting, public speaking, and non-profit work,” he said.

“My journey at Facebook has been incredible and I am very grateful for Mark, Sheryl [Sandberg], and the rest of the team for giving me such an amazing opportunity,” Colleran said in an email. “I take a lot of pride in having been Facebook’s most tenured employee (after Mark) as well as the first member of Facebook’s advertising sales team.”

A spokesperson for Facebook said today, “Kevin played an instrumental role in building Facebook’s advertising business from the ground up. We’re sad to see him go and wish him all the best.”

Facebook’s ad sales team is now led by Carolyn Everson, who replaced long-time VP of Global Sales Mike Murphy. Meanwhile, Colleran’s title is “global sales lead.”

Colleran’s tenacity as a salesperson was detailed in David Kirkpatrick’s book The Facebook Effect, which described him as “a gung-ho cold-caller who could get in almost any door.”

Kirkpatrick reported that Colleran’s first big ad deal at Facebook was a user-acquisition buy by Party Poker, which brought in $60,000 per month (but was dropped due to online gambling regulations). Colleran also led efforts to create sponsored Facebook groups, which eventually became Facebook Pages. An early promotion that Colleran put together targeted Crest White Strips to college kids by offering them Matthew McConaughey movie tickets and the chance to win a concert at their school if they became members of a sponsored group.

Other significant recent or planned Facebook employee departures include VP of Growth, Mobile and International Chamath Palihapitiya and VP of Technical Operations Jonathan Heiliger.

Please see the disclosure about Facebook in my ethics statement.

With that in mind, the company is incentivizing developers to create useful applications with its new Great Apps program. Great Apps, Ben Ling, head of Facebook Platform Product Marketing says, recognizes applications that are meaningful, trustworthy and well-designed. Apps that hew to Facebook’s “Guiding Principles for Great Applications” (see image below)–they must be “social, useful, engaging, expressive, secure, respectful, transparent, clean, fast and robust”–will be given greater visibility across the site and early access to new features. The first apps to be awarded that status: iLike and Causes.

Facebook, it should be noted, plans to aggressively police its site for apps that abuse user trust and will take “enforcement actions” if necessary.

Tomorrow, when it rolls out its new platform, one of the more interesting pieces of news from Facebook will be its initiative to dub certain of its third-party app developers more special than others.

According to sources, the social-networking site has selected just two, in fact, iLike and Causes, to receive “preferred” status.

Several sources said that this initiative has to do with developing in a way more in line with the goals of Facebook Founder and CEO Mark Zuckerberg.

Some issues Facebook has had since unleashing third-party applications on its platform last year have been related to the widgets producing too much spam, not having adequate privacy protection and simply being too buggy.

Included in the criteria for inclusion as a preferred partner is being “meaningful” and also not having been in violation of a wide range of Facebook policies in the past. Individual apps can be approved, even though others made by the same developer might not be.

Causes and iLike are the inaugural partners in the program, with others to follow.

Perhaps more interesting about this move is why two of Facebook’s major developers, Slide and RockYou, are not part of the preferred program.

The pair that have been are among Facebook’s most popular.

iLike is a hugely popular music discovery and sharing service (I will be posting a video of my visit to its Seattle offices tomorrow) and Causes is an app that allows users to share information about various charities and social initiatives.

Facebook declined to comment on the initiative.

But it surely will tomorrow. Facebook is in the midst of a major redesign of its service and will be mounting its second developers’ conference tomorrow in San Francisco.