why would u even ban them in the first place? its ridiculous and pointless, personally I don't have blackops but I know for a fact on the ps3 the matchmaking is poor, so what does one do when he finds a shit lobby? He leaves, but is then forced to wait 5 minutes. By extending the wait, will decrease the amount of potential users for the next game, especially drastically as you put it (hours?! seriously? lol). Fair enough it's a game, but you bought it, you shouldn't have to suffer and wait because of some idiot with a shit connection, and I have raged quit in other COD's, so I doubt this will make people calmer, or make them stop rage quitting, personally I have anger issues, so if I have to wait for a lobby because the lobby was full of MLG snipers then it will make me angry, and I will end up playing either killzone or battlefield, rather than COD. Atleast with those games they don't force you to wait.
you don't get probation for leaving 1 game lol.. even 5 in a row probably you won't unless you're some chronic quitter. if you're so bad that you need to constantly leave lobbies to do well, then it would do you good to stay in them instead :|