Drysc discussed how the ELO system works for arena combat in WoW. Seems like there is finally a system that rewards skill instead of time invested.

With the ELO system your wins and losses are dependent upon your team's ranking as compared to the ranking of the team you're winning and losing against. The system encourages playing as few games as possible (in this case 10) and playing them well. As you begin to play past those 10 your chances or losing and either losing progress or even ending up lower than if you had stopped at 10 begins to rise rapidly. If your team plays your 10 games and you do well and continue to play and win then you're going to rise through the ranks quicker, and it's probably deserved as you're not losing. However, if your team loses a game you're risking a huge setback.

The first couple weeks of each new season is going to see some rapid movement as all of the teams settle into their general ranks. If a team tries playing as many games as possible in attempts to beat the odds it's likely that you'll see them cut back in future weeks as the payoff is usually going to be minimal and the risk extremely high.