There is video of "rainkhan" playing about 28 at once. He claims he has done more though. I looked him up and he is actually -40K on SNG's on pokerstars. so not sure why he brags about how many he can play. He used to play smaller games, now it looks like he got bigger and it cost him in SNG's.
He is up alot on MTT's though so def a good player.