If you think it's that easy for someone to duplicate the idea... is it that special to begin with?
Context: I've been involved in online communities since 1985, as active participant and community leader/organizer/sysop. A subset: BBSes, Plato Homelink, CompuServe, AT&T Interchange, email lists... and that just takes me to 1993!
There has to be a reason for the community to exist. It rarely has anything to do with the UI or the technology foundation; it's all a matter of connecting "like minds."
Starting an online community is like opening a restaurant: There has to be a reason for people to show up. When you've got it, then you don't have to worry about anybody else. When you don't, the competition doesn't matter.