GM tomfoolery. If you're in an RP, and the GM comes out with the following nonsense, then you're doomed:

"I'm going to give some of the others a chance to post before I post again" Translates into "I've lost inspiration for my own idea and can't be arsed, but luckily there's 2 possible MIA players that haven't posted yet so I can use them as a stop-gap on the hopes my inspiration will return!"

"Sorry for not posting, personal stuff has come up, blah, blah" Translates into "Yeah I'm not feeling this, better hit 'em with the age old 'personal problems' excuse. No one will question it, and after a couple of days, I'm free!" 

"I'm going to take more a Game Master role from now on, as [insert possible life interference] is taking up too much of my free time." Translates into "I'm bored and have lost inspiration but feel too ashamed to openly admit it, and will allow the RP to die quietly in the night." - Can usually be debunked by looking at their profile, and watching them shamelessly introduce themselves to other RPs. 

GMs are the same as players, in the respect that they suffer from the whole "Quick Burn" excitement of an idea. They can't find what they want, so they make it themselves, float the idea, get the interest, and then after a couple of days they'll get bored and start making their excuses.