You're right it wouldn't need to grow to the size of Twitter to be successful, but I don't see how it would grow beyond the HN set (and just a subset then). I c

You're right it wouldn't need to grow to the size of Twitter to be successful, but I don't see how it would grow beyond the HN set (and just a subset then). I can't think a single reason anyone would pay for Twitter, when free Twitter already exists. The only pain point App.net really covers is for 3rd party devs who want to quit their day jobs to sell Twitter iPhone apps but can't any more.