How will you get the initial user base and overcome the "ghost town effect"? This is the major problem for any social network / site. Nobody will use it unless

How will you get the initial user base and overcome the "ghost town effect"? This is the major problem for any social network / site. Nobody will use it unless they see that many others are already using it. What's your plan for reaching a critical mass of users before you run out of money to operate and develop the site?