Its not their servers you are using, it uses peer 2 peer hosting, meaning the person with the best connection is elected the host, its just like how the console version works, the highest amount of people in a game is 9v9. The problem with peer 2 peer hosting is, it gives the host an advantage over all the other players, also if the host leaves the game and there isn't another player in the game that can actually host it kicks you out of the game, and you would have to go through matchmaking again to find another game.