As a result of the experience system changing you don't lose anything if you leave a match but if you leave enough matches you will be warned to not leave a match again or you will be temporarily banned. This system kinda works except for the fact if all of your teammates leave and your left in a 1 vs 4 match its not really that fun for either side. In my opinion if all your teammates leave it should prompt you to decide if you want to Forfeit the match and it not go agianst your record for quitting games. 
 
Sure your going to say, just don't quit any other games and your be fine. But in my case my network once in a while cuts out and causes me to disconnect which did cause me to get temporary banned even tho its not suppose too and there has been games where the other team has been considerably better than ours and its either leave the game or I might break my controller. 
 
Overall its just really not fun when you have 8  minutes left in a game and its a 1 vs 4.

I would agree with the 1 vs 4 comment but that's the only time i think you should be allowed to quit without some sort of penalty. Much like Halo 2 and 3 people decide they don't like the game type and quit before the first round even starts......screw quitters.

I just noticed i totally fucked the title in regards to spelling. FUCK! lol

only if they accompanied the forfeit button with the other team executing the forfeiter by firing squad

That'd be okay, I guess. If say half the team wants to forfeit. 
 
I did do a post a few days ago saying that you can still have fun even if you're out-numbered like this. Grab the cloak, if you can, and be stealthy. Try picking them off one by one. 

Definitely in the case of quitters on your team.
 
A message should come up telling everyone on both teams "soandso are quittters and fucktards" and then the game should end.
 
Reach also has problems with members of one team getting all the vehicles and then the game being decided from there.  Until that is fixed I won't be playing team based modes :/