In an Xboxlive game with a Matchmaking system, and you enter with one more person that a team can hold, Its a game of roulette on who is on the other team.
GUY 1-"Ok, guys. Theres 5 of us going into a 4v4 playlist. Someone is going to be on the other team."
Guy 2- "NO! I've fallen prey to that old matchmaking roulette."