I think you can re-phrase your question of "Would I pay $50/year for Twitter" as "Would I pay $50/year for something like Twitter, when Twitter is already free"

I think you can re-phrase your question of "Would I pay $50/year for Twitter" as "Would I pay $50/year for something like Twitter, when Twitter is already free". App.net needs to be considered in the overall market, not as a stand-alone. It's biggest threat (I don't think) is the $50, it's going up agains a free established major brand in a network play. Has this ever been done before?