Comment by permo-w

the solution there is to not ban sites, but simply deprioritise them for a while. you get caught being naughty, your entire domain gets hit with a nasty downranking that gradually decays. put a little flag next to the link explaining to the user why the result is so low. except that the second thing will never happen because it seems that Google policy is to keep search users as powerless and uninformed as they possibly can.