It's acquisition week in Silicon Valley. Yesterday CBS acquired Last.fm and now eBay has announced it will acquire StumbleUpon, the social bookmarking/search engine service, for $75 million. [The deal][1] will give eBay access to almost 2.5 million registered users, though it remains somewhat unclear as to what eBay plans to do with the site. StumbleUpon's founders will become eBay employees and eBay's Michael Buhr will head up the management, but so far no changes have been announced. If you're not familiar with Stumble upon, have a look at our [review from last year][3] and be sure to check out [Epicenter's coverage on the announcement][2], which offers some speculation on what eBay might be planning to do with StumbleUpon. [1]: http://investor.ebay.com/releasedetail.cfm?ReleaseID=246467 "eBay Acquires StumbleUpon" [2]: http://blog.wired.com/business/2007/05/ebay_acquires_s.html "EBay Acquires StumbleUpon For $75 Million" [3]: http://blog.wired.com/monkeybites/2006/10/the_social_book_3.html "The Social Bookmarking Showdown: StumbleUpon"