They were building a social network, then it became an ecosystem - I just can't see any economy out of it other than paying users paying for it to tweet each other in more than 140 chars. Oh, and now some free users too(which includes yours truly; I tweeted there once).
That's what I don't get. Seems app.net wants to be something to everybody. Not that I haven't done that very same mistake myself. But you you have to start small/scrappy and build up features. It's the only way.