Lurkings in the Dark
At this point, just one player. I do not want to mess with multiple players and multiple posting rates. For now, we post at leisure and see where it goes.
An idea I hit on is the concept of players sponsoring other players to come into the game. They make the recommendation for an new player and they have a lingering responsibility to keep that player active. I am not sure it will work, but I like the idea that player1 will think hard about inviting player2 if in the long run he does not think player2 will stick it out. He has to harrass the player, not the DM (the DM is just responsible for any core players he invites). It creates a club/ownership concept that might up the dedication.
Plus, since it is Cthulu, it really is easy to get rid of an orphaned PC