I'm a member of a number of Facebook groups, and, while I consider them useful, they are also incredibly irritating. Everybody already has a Facebook account, so joining a page is as simple as clicking "Join."
I have to manually approve every newcomer here so that we can avoid spam. We get several a week. That being said, I do basically nothing to advertise so it's all organic growth.
Every site fills a niche; what niche does this site fill? Well, it's up to you, the users. I created it...4 years ago, now? It was an experiment out of the ashes of "TrumpetMaster."
It costs me something like $30 a month to run, and I can write that off my taxes because I don't make a profit, so it's essentially a "community service." I'm not too worried, and we have had some generous donations over time so it all balances out. That being said, I would take it down if nobody were using it. So, keep using it.