When discussing World of Tanks on this blog, several commenters stated one of the oldest myths of team-based gameplay: If they win it is because they are so good, if they lose, their team was bad. The same thing is often being said about pickup groups in World of Warcraft. But it is extremely easy to show mathematically that a "bad team" is so extremely unlikely as to be a very bad excuse for losing.
Imagine you could classify players as either good or bad (which as discussed earlier is a myth by itself). Now randomly draw 14 teammates for your World of Tanks team. What is the probability that you end up with a completely "bad team", with 14 bad player team mates? It is 1/2^14 = 0.006%, something which only happens once in over 16,000 games. And then of course you have to assume that the enemy team has all the good players. What are the chances of that? 1/2^29 is a one in half a billion chance!
Mathematical fact is that if you draw random team members, in 95% of the cases you get a team which is average, plus or minus 2 sigma (standard deviations). The overwhelming majority of battles in World of Tanks pitches two completely average teams against each other.
It is unfortunate that some people have so little real world achievements that they consider their skill in video games to be the source of their self-worth. These are the people you see arguing all the time about how valuable video game achievements are, and how games should have systems that favor the elite gamer. But of course if you believe that your greatest achievement in life is being an elite gamer, a perfectly balanced PvP game is the last thing you want. The myth of the bad team is needed by these people to preserve their illusion of self-worth. They could never admit that sometimes in a game you just make a bad move and lose, because that would go to the core of their being. Fortunately there are now specialized psychiatric clinics for people with this sort of mental defect. Until they seek help I'd advise them to stay away from team-based games. A team-player by definition works well with the other people on the team, and doesn't just need them as an excuse for losing.