Xobni has been acquired by Yahoo!  The company, from YC S06, made the announcement today on the Xobni company blog.  Xobni “makes your inbox and address book smarter by making it easy to search and discover all your contacts.”  It provides “a full view of each contact, complete with their photo, job title, company details, and email history — as well as updates from Facebook and Twitter.”  When it launched in 2008, Bill Gates did an on-stage demo of Xobni integrated within Microsoft Outlook.

Jeff Bonforte, Xobni’s CEO, will be returning to his former employer with this acquisition.  Prior to Xobni, Mr. Bonforte worked at Yahoo! in the positions of both Vice President of Social Search and V.P. of Real Time Communications.  Based on that history, All Things Digital reports this acquisition was of particular interest to Yahoo co-founder David Filo.

Multiple sources, including Wall Street Journal and VentureBeat, estimates the purchase price between $30 million dollars and $40 million dollars.  BusinessWeek and TechCrunch both estimate the purchase price between $60m and $70m after “earnouts and other considerations”.  Since completing Y Combinator in Summer 2006, Xobni has received more than $40 million in funding.  Therefore, the $60 million dollar estimate seems more likely.

In a new support document posted today, Xobni states new purchases of premium products are no longer being accepted, Smartr Contacts for Android and Xobni for BlackBerry are discontinued, and existing users will receive support through June 2014.  This is Yahoo!’s first acquisition of a company funded by Y Combinator.  In contrast, Google has acquired 7 YC companies, Facebook has acquired 6 YC companies, and Twitter has acquired 4 YC companies.