Comment: Take it a step further--after you've institutionalized the cat-feeders, re-purpose the feeding stations as BAIT stations.  Baiting is illegal for taking most big game (except to a limited degree for taking bears in my home state of Alaska) because it works so well it's almost cheating.  Cats aren't game--they're vermin.  Bait the cats, shoot every one that shows up to take the bait.  Rinse and repeat until no more show up.  Pay attention, cat-nutters!  Here's a way for your so-called "vacuum effect" to achieve something worthwhile!