So I still play quite a bit of StarCraft online. I am not great at it (low Diamond league) but I am good enough at it to know when I'm playing a Smurf.
A Smurf is someone who is deliberately playing in a league far lower than what they should be in and they really ruin the game experience.
Smurfing isn't specific to StarCraft and there really isn't much that can be done about it that I can think of. But it is one of those things that helps remind me as to why I don't want to develop games that rely heavily on competitive multiplayer.
If I play 10 games of StarCraft the breakdown is something like this:
2 games will involve Smurf accounts outright
1 game will probably be a smurf but can't tell because they immediately quit
1 game will involve some sort of obnoxious cheese strategy (as you go up in rank, this becomes less common ironically).
1 game will involve griefing. This isn't "cheese" per se because they aren't really trying to win as much as make the game unpleasant for you.
1 game will involve a ton of BM that forces me to mute the player.
4 games will be actual, legitimate games.
The only thing that saves StarCraft is that even though only 4 of the 10 games are real games, those games represent the vast majority of actual play time.
But the % of games that involve some sort of social-path spectrum player is sufficient to make me wary of ever wanting to make a game for that genre.