I bet a similar trick was done to start sites like Digg or Quora. Any social-based site needs initial momentum and content to attract real users, so someone nee

I bet a similar trick was done to start sites like Digg or Quora. Any social-based site needs initial momentum and content to attract real users, so someone needs to provide it first... Can you present any other examples, especially re: marketing your own social-like startup in this way? That might be interesting.