Not HN, but this thread on Quora will be useful to you http://www.quora.com/Startup-Traction/How-do-social-sites-%28examples-Hunch-4Square%29-go-from-1-to-100k

Not HN, but this thread on Quora will be useful to you http://www.quora.com/Startup-Traction/How-do-social-sites-%28examples-Hunch-4Square%29-go-from-1-to-100k-users-What-techniques-methods-are-used-to-grow-early http://www.quora.com/Startup-Traction/How-do-social-sites-%2...