Drives me nuts, too. For one thing I'm downright saddened that the Survivor game doesn't look like a go... There was a lot of initial interest, but then suddenly it sinks away. Very disappointing. I could try running it with fewer players, but then I'd have to rework the challenges I've already gotten planned for it, and four players at a time was already a little scant on the competition element.
There are three more I've signed up for that never started... Game of Opposites: Villains is in the abyss (although the hero thread is going, which is confusing), Game of Elves had a lot of interest, but I think I'm still the only one to put up a character sheet... I inadvertently got included in the four-players-versus-the-dragon game, but once I was in I spent a good amount of time putting together what was IMO a pretty whoop-assing dragon-slayer.
Not sure why this happens, exactly. A Game of Trust was an instant go, and I think its design may have contributed to that: There was no signing up period, it was just the first six people to post in character. I've lost two players since then, but the ones who remain all seem pretty dedicated -- or at least they have some really well personified characters.
I think that may be a fluke, and the opposite is still more what I'd suggest: Keep slots open until people submit full characters, including background. This deters the impulse "I'd love to play!" posters, and means that the roster doesn't get full until there are x number of people who have actually put some kind of investment into it.
