Reports surfaced earlier that Twitter may be acquiring AdGrok, makers of an AdWords keyword tool, but AdGrok has now come out and made it official. Starting today, the team (2/3 of it anyway) will be working full-time on Twitter’s revenue engineering team.

Matthew McEachen, and Argyris Zymnis of AdGrok are now part of Twitter, while the other third – Antonio Garcia-Martinez – has joined Facebook.

“When Twitter approached us and asked if we’d be interested in working on their monetization platform, we realized that this was a once-in-a-lifetime opportunity that we just couldn’t pass up,” the AdGrok team said. “The fact that the Twitter team is both smart and user-focused only made our decision easier.”

Meanwhile, the team is will be shutting down AdGrok itself. Here’s what they had to say about that:

We are no longer accepting new customers and will cease charging our existing users immediately. We will shut down our servers on June 30th, after which the GrokBar will not be available. Uninstalling the GrokBar is easy: http://adgrok.com/help#uninstall

Please note that performance data and campaign structures from the campaigns you have run through AdGrok will not be affected by the shutdown of our servers; this information will continue to be accessible through your Google AdWords and Google Analytics accounts.

The acquisition is rumored to have been for under $10 million.

Twitter is also expected to be launching its own photo service, which could spell trouble for services like TwitPic and YFrog.

Last week, the company acquired third-party Twitter client TweetDeck.