StumbleUpon, the toolbar used by thousands of people to share sites they find interesting, may be in acquisition talks with eBay. The rumor mill has suggested Google and AOL may also be interested, but Mike Arrington from TechCrunch says a term sheet with eBay has already been signed. Estimates from Mike and Om Malik place the price between $40 and $75 million.

StumbleUpon allows people to rate websites and learns what type of sites particular users enjoy. In a moment of boredom, any user can click the “Stumble!” button and they will be directed to a page that the system believes they will enjoy. StumbleUpon has a strong following from it’s users and very few competitors.

Mike Arrington has been trying to reach someone at StumbleUpon to confirm this acquisition but they have yet to respond (which leads him to believe it’s golden).