The Journal has a nice piece about how eBay's realizing that it's market reveals information about preferences that is valuable - so it's starting to develop new, more stringent licenses for it.
"...EBay provides a clear window into the steep decline in the price of most secondhand electronics, which quickly lose value as new gadgets appear. Just after it was released in February of this year, the Nokia 3650 -- a cellphone with a color screen -- sold for an average price of $400 on eBay. By July, it had fallen to an average of $245 on the site and this month it is selling for about $225."
I think this is cool, but there are two issues. First, the info that's revealed is subject to some of the common problems with simple auctions, like the winner's curse, etc. Second, what eBay should really do is cut transaction for people who want to use the data - maybe by developing APIs and a standard royalty/license scheme.