There are numerous forum threads on this topic, pullinup. Use the search feature at the top right and search for 'quitters'; then have about a day and a half to wade through all of the threads and suggestions.
WGT has shown no interest in addressing this up to this point, but I completely agree that a user-defined ignore list would be a GREAT way to allow each and every player to decide who they wish to weed out of their game searches. This too has been brought up in previous threads, you'll see if you search and look in to it.
I've thrown this out before also, and would love the ability to block other players from my wall, not see them in the forums, etc etc etc.....