Multiplayer team games are all the rage nowadays. From a cynic's point of view, they're the natural solution to the AI problem (just use other real people instead), the content generation problem (let people create their own stories by interacting with, yes, real people) and, tangentially, the DRM problem (enforce a requirement for online play, then either host a lot of the content on remote servers, or just ban clients which you don't think are authentic).
For players, multiplayer team games also enhance the experience of the game by adding some vestige of a social element. Even "dumb" team shooters - like Unreal Tournament 3 - allow some aspect of this, through both public (and team) chat, the addition of voice comms, and the simple nonverbal forms of interaction (even griefing is a social interaction, albeit an essentially disruptive one).
The problem is: all those guys who got picked last for teams at school.
The point of a game, arguably, should be to have fun. The point of a team game is to have fun with your friends. And, some of fun of any game is from achieving the victory conditions formalised by the game itself.
So, that allied medic who's so bad that the enemy keep killing him before he can heal the rest of you can be really annoying. As is the sniper who can't hit anyone for toffee, the spy whose actions scream "enemy" to anyone who watches him, the player who insists on using the explosive weapons at point-blank range. And so on.
Now, imagine how they feel. If they have half a brain, they know they're the weak point in their team, the ball around the collective leg, hauling everyone else back from the brink of victory. Maybe they've picked a support class because they know their aim is terrible - but so's their evasion, unfortunately. Maybe they're actually trying to practise, but in the process are sabotaging their team's chance for success. Maybe they're just never going to be that good. Whatever the reason, they're trying to fit in, to help, to have fun with the rest of you, but it just isn't quite working.
It's hard to have fun when you're leeching away (perhaps ever so slightly) at everyone else's.
So, why don't they just go and play on the talentless servers? (You think, in frustration at the useless guy being one-shotted for the nth time.) Maybe they do. Maybe there aren't really any talentless servers left - almost everyone who plays the game has reached their comfortable level of competence, and most of them are better than this guy. (Maybe he's trying to stretch himself.) (Maybe, as with MMORPGs generally, there's no such thing as a talentless server.)
For the these losers - the guys who would be metaphorically picked last for the team - the rise of the multiplayer team game is the worst possible result. Social interactions thrive on in-group and out-group classification, and someone always has to be in the out-group - which is also the least fun place to be. Human nature breaks the team game, makes it something judgmental (if only implicitly), and confidence-sapping in the worst instance.
If we play games to indulge in power fantasies, the worst nightmare is the one in which everyone else gets better powers than yours.
Is there a solution to this? Probably not, without reworking human nature itself. Perhaps, though, a resurgent focus on single-player games, and sole-player paths for MMO-style games, would be an adequate solution - if you can't mix it with the cool kids, you can at least have fun the way games used to be played - comfortable by yourself.