Teams are a pain in the buttox, and I blow up with anger when dying by one.
It's not even MCSG, alliances in FFA gamemodes all-around grind my gears, but I understand why they do it, and it's to win. Cheap or not, the goal of the game is to win, and as long as you're in the boundaries of the rules, then it's fair game.
Restricting teams for the Top 100 would be more of a punishment, rather an accomplishment to hit the 100. It's almost like segregation, if you're good at MCSG you can't play with friends. That's not fun or fair now, is it?
Teams are annoying, but you have to keep them for entertainment value.