I have two major problems with RPs as they are now. The first one, obviously, is the lack of long term commitment, of which I am occasionally a guilty party myself. Most RPs fizzle out as people lose interest, get busy, etc. I once had an idea to start doing shorter, more focused RPs but no one was active at the time anyway so it was rather a moot point. I'm talking RPs with a small group that take 50 posts or less to finish. Something like mission based RPs, like someone mentioned above. Or maybe RPs with lower stakes--not necessarily saving the world so much as saving one's own skin. It would also help if RPs could be more dynamic and not sorted so much into epic war, quest and good/evil type stories. But I suppose that latter bit is more of a personal preference.

The other major issue I have with RPs is that unless the RP is invite only, you always get that one wanker (sometimes more than one) who joins and is either on the other side of the virtual map doing their own thing and contributing nothing to the story or they simply aren't at all serious and start introducing ridiculous concepts that completely go against the grain. That's what happened to my Sky City RP, which sucked because I'd wanted to do that one for years.