Echoing and continuing on Dan's point: I'm also a member on the MaxFun boards and some other active and sizeable-yet-closeknit community sites (that have spawned member-meetups, or bigger events like MaxFunCon) and like Dan said, a very important element is activity and accessibility from the site staff and/or hosts. In addition to regularly posting on the boards, making yourself available to people and encouraging them to get in touch. Jesse and Marc Maron regularly announce their personal email addresses on air, and Jesse's site has private user mailboxes/messaging as well as his email addy posted there too. On geekier sites like Metafilter, the owners also include AIM/chat/Skype contact info.
I've already tried to get active here offering design feedback and tipping off the staff to minor site/server bugs both on the forums and via the contact form, and haven't received anything more than an automated response email with no reply address (I know you're really busy and the site is very young, so it's no biggie - just emphasizing my point). I understand if the hosts are too busy to be involved a lot, but at least the crew should be more accessible, maybe private messaging to site users should be implemented, and everyone on the earwolf team should be posting at least once a day somewhere on the forums just so folks know that they are listening and making an effort to build the community. Theoretically internet communities can build themselves unmonitored, but from past experience, some community moderating and a lot of active participation from the owners makes for much better experience for everyone.
And lastly, I disagree with the idea that you shouldn't need a site account. It's a little annoying at first to sign-up, but going through the process gives you more incentive to come back or make use of the account you created. Having instant access via facebook makes it more disposable, plus you'll get a lot of extra lazy comments and trolling from passer-bys who are not willing to be active community members. People who use the site will soon forget about having to sign up and will enjoy having their own account on a site they value.