Its action is quite different to Google’s recent efforts to foil the PageRank scammers. Google ranks its results and gives each one a PageRank score. Over the years, spam sites have learned how to twist Google’s rules in their favor, gaming the system so that their sites naturally rise to the top of the pile. Google’s reponse was to re-set their PageRank, lowering their score so that their clickthrough traffic (and therefore their income) shrinks enormously overnight.
Blekko, on the other hand, has written a separate algorithm it calls AdSpam. Rather than lowering the score of suspect sites, AdSpam seeks out dodgy search results and simply deletes them from Blekko’s database, so that they never get shown to users at all. It has help from human curators, in an attempt to ensure that genuine sites don’t get Blekko-zapped by mistake.
It might sound like a draconian solution, but with internet traffic only increasing, the spammers will go to great lengths to ensure their sites attract clicks. The search engines must go to similar lengths to fight back.