Faking it.
This is more or less what I did with my site, Scribophile.  The site is based on writers critiquing the writing of others, with a point system to make sure everyone gets critiques.  When I just started, it was kind of a chicken-and-egg problem: without existing work to critique, nobody could earn points to post their own writing; but without points, nobody could post their own work for critique.  And worst of all, without an existing user base, there would be nobody around to critique writing that was posted.I solved this problem by basically faking it.  When the site just started, I let people post writing without spending points.  I would then personally critique that writing myself through several fake accounts.  These critiques not only made new members feel as if there was already a community in place (thus encouraging them to stay), but they also made sure that people felt as if the site was useful, and made them want to contribute with critiques of their own.  I don't write for pleasure, but I posted some works I had written just for the occasion.  I didn't care about the critiques they received; the important part was making people think there was a community already there.  I also recruited some friends who weren't really writers to participate on the site at the beginning to solidify the illusion of an existing community.I also had a general "company" user account that I used to interact with everyone on a site-support level.  This gave the illusion that there was more than one person behind the scenes.  At the time I felt that having a web site that seemed to be run by a proper company instead of a guy in his basement went a long way for credibility.  I never gave away the fact that it was just me.  I would sign all support requests with "Scribophile Support" instead of "Alex."As time went on and the site grew, I stopped critiquing by hand, thanked my non-writer friends for helping me and told them they didn't have to participate in the site any more, and eventually stopped using the "company" account in favor of my personal one.  Everyone now knows that I'm the owner of the site and the guy behind the scenes.  I sign support requests with my name instead of "Support."I have no doubt that if I hadn't "faked it" in the beginning, the site would never have gotten the traction that it now has.  It was essential for getting a community site bootstrapped with a $0 marketing budget and the chicken-and-egg problem that all community sites face.