And that trigger can probably happen any time something new attracts a critical mass of early adopters; then the network effect of the walled garden actually be

And that trigger can probably happen any time something new attracts a critical mass of early adopters; then the network effect of the walled garden actually become a detriment to the old network as it enables rapid defection to a competitor. People have been dismissing geek-centric alternativesl like Diaspora for having a built-in limitation on growth, but most communities on the internet - and the internet itself - grew out of geeks gradually building up enough of a user base to pull in everyone else. Maybe it just takes time. BTW, I received my first Diaspora invite this week.