IIRC almost every online game for the Xbox 360 uses the P2P strategy (which is funny, given that Microsoft charges for online), so I wouldn't say that it isn't

IIRC almost every online game for the Xbox 360 uses the P2P strategy (which is funny, given that Microsoft charges for online), so I wouldn't say that it isn't common or viable. You don't see it as much in PC games because PC gamers are more capable of running their own dedicated servers, which provides a superior experience while still shifting the burden from the developers to the players. P2P is still the norm for genres with small numbers of players per game (1-on-1 fighting games, co-op games with small parties). EDIT: I'd assume the reason that games like LoL don't use P2P hosting is that the games are competitive and ranked, and having players host in any fashion would make it all too easy to cheat your way up the leaderboards.