Why Does eBay Want StumbleUpon? To Promote Its Auctions
At first it didn't quite make sense to me why eBay would want to acquire StumbleUpon. eBay does auctions and sales. StumbleUpon does random entertainment. At least, that's the way I used the two sites.
But then, of course, I remembered that StumbleUpon is basically just a huge database full of associated interests. It's kinda like Amazon. People who liked X also liked Y.
Deploy that technology on eBay, and suddenly your users find all sorts of stuff for sale they never knew about. I imagine somewhere inside eBay there's a chart showing that a huge percentage of their site is basically untrafficked. StumbleUpon, if deployed correctly, would help.