Another open secret becomes official ... Google has acquired RSS distributor FeedBurner and its FeedBurner Ad Network, filling a significant gap in its own advertising offerings. No terms are being disclosed officially; the deal already has closed. The reported price when the most recent round of reports started: about $100 million.

From the official FeedBurner blog: “We are confident that we are going to be a part of the company that can best deliver the most comprehensive suite of services to publishers.” Susan Wojcicki, VP, Product Management, wrote about the acquisition at the official Google blog.

There’s also a FAQ that includes this answer to the why question: “Google believes that feed-based content and advertising is a developing space where we can add value for users, advertisers and publishers. FeedBurner’s technology and talented team are a great addition to Google’s current solutions for advertisers and publishers.”

Some mixed messages on autonomy and the future. Here’s the FAQ on the subject: “Q. Will Google assume full operational control of FeedBurner, or will FeedBurner remain autonomous? A. We are excited to have the FeedBurner team join the Google team. The FeedBurner website will remain operational as we continue to integrate their technologies with Google’s tools.” Another answer says it’s too early to tell how FeedBurner will be integrated and another says FeedBurner will continue to sign new users.

Lots of red flags already flying from privacy watchers. Here’s the FAQ: “We believe that notice and choice are the foundations of privacy. As such, we are committed to transparency for our end users, and to respecting the choices they make with regards to their privacy preferences. The transition to Google’s privacy policy and the opt-out mechanism we are providing for current FeedBurner users will help us achieve these goals.”

As of February 2006, FeedBurner had $10 million in investment backing. Investors included Mobius Venture Capital, Portage Venture Partners, Sutter Hill Ventures, Draper Fisher Jurvetson and Union Square Ventures. Based in Chicago, it was founded in 2004 by Dick Costolo (CEO), Eric Lunt (CTO), Steve Olechowski (COO), Matt Shobe (CDO). More than 431,000 publishers (including our parent, ContentNext Media) use the service.

Update: About that opt-out mechanism ... I just logged in to our FeedBurner account and a note came up explaining service would not be interrupted because of the acquisition but we have 14 days ending June 15 to opt out of allowing Google to service the account. The alternative: “If you take no action by June 15, 2007, the rights to your data will transfer from FeedBurner to Google. Opting out will terminate your user agreement with FeedBurner, permanently delete your FeedBurner account, feeds, and all related statistical data and history, and prevent the transfer of your data rights to Google.”

Update II: AP: “Google will allow FeedBurner to remain based in its current Chicago headquarters, but hasn’t made a decision on whether the brand will be retained.” FeedBurner has 30 employees.