Please get off the "twitter clone" smackdown ... it's lame. App.net is a trustworthy "blackbox" which allows ANY social construct. It dovetails with Tent.
People are building Tor concepts, non-Zynga collaborative games, new messaging protocols, etc in App.net ... beyond twitter is easy. Indeed, it's hard to keep up with all the API enhancements, and the new developer ideas. My personal goal inside App.net is a construct which brings down the GFW (firewall) of China. (Im fluent in 中文, 25+ years).
No advertisements, paying developers well. Integrity about the future ecosystem. With a $1 million in the bank, one of the best geek hangouts on earth, and world-class integrity ... it ain't going away in months.
You'd be better off predicting that it's a heady time for new social protocols.