The yellow-handled hammer, which the eBay CEO purchased at Home Depot using PayPal, signals that the company’s plans for entering the mobile payments business has entered the construction phase.

In an interview yesterday, Donahoe provided a few details about the company’s Home Depot trial and how it would expand from five to 51 stores across the country over the next week.

He also talked about his own experience of buying the tool earlier that morning. (Seen at right: Donahoe wielding his hammer.)

The company also announced fourth-quarter results yesterday, solidly beating both the company’s internal guidance and analyst expectations.

One of eBay’s big initiatives over the past year has been to find ways to work more closely with physical retailers by providing them with the technology they need to operate more efficiently online and offline. Over the past year, that has included buying 13 companies, for a total investment of $3.4 billion.

“We are right at the intersection of something that’s really cool,” Donahoe said. “This isn’t something that everyone sees, like social networking three years into it, when only the early people knew about it.”

What everyone is not seeing, he explains, is how retail and payments are two massive industries that are “at an inflection point where they will go through dramatic change.”

One major opportunity is payments being made at the cash register, and arguably many others see it, too, including Google, Visa, MasterCard and the wireless carriers, which are all working on their own solutions.

Interestingly, Donahoe was willing to put a price on it — and it’s huge.

If eBay is able to capture just 2 percent of the sales occurring at the point of sale, it will be able to double PayPal’s $70 billion business today. If they capture 4 percent, they’ll triple it.

Of course, that will take some time.

This year, eBay is focused on learning and testing out the technology in several trials; then, in 2013, it will begin to scale the business. In 2012, the company is not even factoring in a lift from point of sales in eBay’s revenue guidance.

The company’s big test will start later this week, when it expands its trial with Home Depot from five stores in the Bay Area to 51 stores in the Bay Area, Atlanta and Omaha.

Everything continues to be on track, despite the unexpected departure of PayPal President Scott Thompson. Thompson shocked Donahoe right after the New Year with the announcement that he was leaving to become CEO of Yahoo.

Donahoe declined to give an update on his plans to replace Thompson, saying that he was fine with serving the interim role in the meantime, and relying on the rest of the team PayPal has in place.

So far, Donahoe said, the mobile payments technology works flawlessly, based on his own experiences, but there’s still some additional scenarios they will have to consider.

Yesterday morning, he drove to a store in San Jose, where he consciously left his wallet and phone in the car.

He walked through the aisles to find a hammer and tape measure, and then went to check out, where the terminal gave him the option of checking out with PayPal. He entered his mobile phone number and PIN, and the transaction was completed, with the receipts sent to his phone and email.

“It was faster than swiping the card,” Donahoe said. “This is an advantage that PayPal has. No one else can do it with a mobile number and PIN. There was no fancy whiz-bang technology.”

Customers will also be given the option of paying with a PayPal credit card.

But not all the pieces are in place yet.

Coming soon: Users will be able to store their loyalty cards in their PayPal wallet, and will be able to receive personalized offers based on their shopping habits.

Also, it’s worth noting that while Donahoe checked out easily, there will be a learning curve for others. In advance of going to the store, users will have to associate a phone number and PIN with their account, and enable their account for in-store checkout.

Right now, there’s no contingency plans for if a person doesn’t have a PayPal account, or if it’s not set up. In fact, a very small percentage of the more than 100 million PayPal users have likely done that.

“That’s exactly why I say this is the year for trialing and learning,” Donahoe said, appropriately adjourning the interview with a bang of the hammer.

That Internet sprite, Groupon Co-founder and CEO Andrew Mason, continued in his quest to be the cleverest little entrepreneur on the Web with a very funny post on the Chicago-based start-up’s blog yesterday titled: “No Comment!”

Mason is well known for his hipster-ironic-cute no-comment responses to the media, such as one he gave the New York Times recently:

“Andrew Mason, Groupon’s chief executive, declined an earlier interview request, adding that he would talk ‘only if you want to talk about my other passion, building miniature dollhouses.’”

Buuuuuurn, NYT!

In his latest rumination on life as a digital celebrity, Mason more fully outlined what he would not comment on, including everything even remotely interesting you might want to know about the social buying company, including:

* Plans relating to capital-raising, including a possible public offering

* Pre-announcements of new products

* Our competitors or the competitive landscape

* Statements on core business metrics, including margins or profitability

* Any projections regarding revenue, growth rates or other financial metrics

*Strategic transactions or partnerships with other companies

Thank goodness any metrics we want about how many discounted stripper pole lessons Groupon has sold in Omaha is on-limits!

Mason–who appears to want to become the Midwestern version of comic Jackie Mason, except Jackie would have taken the $6 billion from Google–is now styling a very scruffy Jeremiah-Johnson beard on this blog post, which you can see above.

BoomTown’s query on that: Why, dear God, why?

Here is Mason’s full “No Comment!” post:

No Comment!

As press interest in Groupon has grown, I’ve found myself increasingly uttering two words that have always annoyed me: “no comment.” We like to be as transparent with our customers as possible, but, just as people don’t walk around naked, there are some things that we as a company don’t talk about (for obvious reasons).

The least we can do is be transparent about the things we won’t be transparent about, which are listed below:

* Plans relating to capital-raising, including a possible public offering

* Pre-announcements of new products

* Our competitors or the competitive landscape

* Statements on core business metrics, including margins or profitability

* Any projections regarding revenue, growth rates or other financial metrics

* Strategic transactions or partnerships with other companies

While we’ll clam up when asked about the above business-y stuff, we’ll always be straight forward about things that affect the experience we’re creating for customers and merchants.

At least for those following the Microsoft-Yahoo takeover battle, since silence is maybe not so golden in this case.

Right now, even though Microsoft (MSFT) set a Saturday deadline for starting its proxy battle against Yahoo (YHOO), the waiting game continues as Yahoo hopes Microsoft will flinch and vice versa.

So, can a fun-packed weekend with the folksy Warren Buffett save the day?

In an unusual bit of timing, both Yahoo President Sue Decker and Microsoft Chairman Bill Gates will both be in Omaha starting Friday for the famous annual meeting of Berkshire Hathaway (BRK-A), which Buffett runs with his longtime partner Charlie Munger.

Decker came onto the board in 2007, while Gates–a close friend of Buffett’s–joined in 2004.

(Gates and Buffett pictured here together; Decker’s head shot here too.)

How awkward is that, since Microsoft CEO Steve Ballmer might be slapping Decker’s boss, Yahoo CEO Jerry Yang, all around Wall Street next week?

At least, the pair are sure to have fun in Nebraska.

Berkshire Hathaway’s annual meeting is a beloved ritual for its shareholders, who flock to worship Buffett every year at the Qwest Center in Omaha.

The festivities will begin on Friday evening, include a “Baja Beach Bash” on Saturday and finish up with dinner at Gorat’s Steakhouse on Sunday evening.

And perhaps Buffett, nicknamed the Oracle of Omaha, might be just the kind of power broker who can finally bring sensibility to the situation.

Celebrated as the world’s most successful investor, Buffett’s plain-talking advice about the stock market is widely quoted.

My personal favorite is “Only when the tide goes out do you discover who’s been swimming naked.”

But maybe this one is more apt, when talking about Yahoo and its value to Microsoft: “It’s far better to buy a wonderful company at a fair price than a fair company at a wonderful price.”

The question for Gates and company–Is Yahoo wonderful or is it fair?

And until Buffett can work his magic, here’s another unlikely pair–Debbie Harry and Kermit the Frog–singing about making nice in the classic, “Rainbow Connection.”