eBay has bought browsing tool StumbleUpon for approximately $75 million; a spokeswoman said the deal was all cash. StumbleUpon lets users rate sites and suggests web pages for users to discover (or, “stumble upon”). The tool works with IE and Firefox and bases recommendations on “thumbs up” or “thumbs down” votes from others with shared interests. It claims to have 2.3 million users who deliver about 5 million recommendations a day and pegs its growth at 150 percent year over year. The six-year-old company was founded in Calgary, Canada, but is currently based in San Francisco.

StumbleUpon was bootstrapped until March 2006, when it raised funding from a number of angel investors, including Google director Ram Shriram and Lotus founder Mitch Kapor. Michael Buhr, senior director at eBay, will serve as general manager of StumbleUpon effective immediately. StumbleUpon’s current founders and management team will remain in their respective positions and will work with Buhr going forward. Release.

From StumbleUpon’s blog: “... we think that joining eBay is the right thing to do to help us to grow StumbleUpon to its full potential. We think eBay is a great fit for us because eBay and StumbleUpon share similar approaches – we’re both driven by our community of users, and we are both dedicated to connecting people.”

Staci adds: After months of speculation, an eBay-StumbleUpon deal was suggested last month, with TechCrunch saying a term sheet had been signed and putting the price between $40-75 million and GigaOm reporting eBay as the likely winner over AOL and Google.

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