Currently I'm DMing 4 PbP games (one of which has two smaller groups instead of one bigger, but they interact with each other often) and playing in 4 PbP games, and within the next month I'm planning to take one PbP game I used to DM off hiatus and join one LJ game. So yeah, 8 games at once, soon to become 10, and I keep full interest in all of them. More than that would probably be too many, though.