Some sort of penalty would be better than nothing. And of course those who have to quit every now and then for legit reasons won't be affected. I'm talking about a system where you'd have to quit say 15 games in 48 hours for any penalties to occur. and even then, it was only a 10 minute ban in reach, so if you had that many legit reasons to quit (although highly unlikely, and if you did, you probably have more important things to do than play halo), it's nothing huge. but it's better than nothing.
Fair enough.
but see, you could complete the previous match without said next horrible player joining that very same game.
oh, and speaking of which, although not a major complaint of mine, just an observation: previously if a player and his guest was playing so bad that it was bringing my game down, i could provoke him to betray me once or twice, then boot him, then be awesome and win the game by a mile. now it's pretty much impossible to betray teammates (unless playing large maps with vehicles). i've even tried throwing 2 plasma, 2 frag, and 2 whatever you call em grenades at a teammate to test it out, nope, he didn't die lol, and this was with explosives perk. i guess the benefits outweigh the negatives in this case though, for most players at least.
How long have you been playing Halo? Friendly fire has only ever been used for griefing in my experience.