Google certainly has the names of all sites that buy and sell links. Google has stored and anylyzed the entire internet to the very max.
Any website has the right to buy and sell links at Google, Yahoo, AdBrite, Textlinkbrokers etc.
But also Google has the right to show any results they want to show. Why should they make links selling sites more popular?
Now with the new link report scheme they can officialy justify penalties or total bans more easily rather than ... dear webmaster, we found out, that you bought 1.000 links at this certain broker ... "