He's relatively plugged into the SV tech scene. He also struck a cord with his original blog post[1]. App.net was obviously just a reaction to the outpouring of support for the ideas he expressed in that post. This could just be proof that 80,000+ page views of a blog post does not equal $500K in paid users at $50, $100, or $1,000 a pop.

More recently he received a ton of attention from his open letter to Zuck[2].

[1]http://daltoncaldwell.com/what-twitter-could-have-been [2]http://daltoncaldwell.com/dear-mark-zuckerberg