Hamlet, Ordinal Malaprop, Rik Riel and others have paid attention to the ad farms littering the SL landscape. There's even a Flickr stream for Griefbuilds, which I contributed to. This plot at Thetidia looks ugly, but is not for sale; apparently the owner is trying to make a few lindens by placing ads on their land? The plot in the back, in Timandra, however is for sale for a cool 28.000 lindens for 512 square meters.. I don't suspect they will be bought out anytime soon.