Maintaining a sense of danger, and getting your players to post
In tabletop RPGs, and computer game RPGs there’s always a risk of your character dying. Players will spend a long time building their character stats, collecting items so the danger of their character death makes them take great care in trying to stay alive.
In play-by-post games, players are in control of the story, and write as if writing interactive fiction. There’s no real risk of a character being killed, unless it’s something you want to happen yourself. Killing other player characters is against the rules (in every play-by-post game I’ve ever seen), so there’s not much chance it will happen.
We all need danger
Danger makes good stories. Nobody wants to read a story about a man walking to the shops to get an ice cream, but if it were a dangerous journey over rivers of hungry crocodiles, past an erupting volcano and past deadly ninja warriors, it suddenly becomes much more interesting.
So there’s a chance that your players might get complacent because they know their characters aren’t really in any danger. Like main characters in a long-running TV show, you know they’re not going to die really, because they’re essential to the show. This doesn’t stop the series writers from putting them in trouble though, and making things extra difficult for the character.
Edit: It appears not long after this website re-appeared, it disappeared again. Rubbish!!!
If you counted up all the play-by-post games that are currently being played across the world today I imagine that a huge proportion of them are spin-offs from Star Trek or Star Wars, and many more based on popular TV series and films. When I first created 
