After joining Flickr (due to this thread) I have gone a bit nuts: uploaded tons, joined a zillion groups, built up contacts, reorganised and renamed pics, and now scanning a few oldies I've not had online before...
However, there is something not really working in terms of community on Flickr. Perhaps it's an issue of scale, or I haven't found the right groups, but there's hardly any real discussions happening. I have seen some wonderful photos and traded a few PMs but it's a tricky place to (virtually) get to know people.
I'm particularly surprised there aren't more photo competitions. I have found a weekly comp on just Babies & Kids that's excellent, and another general comp running irregularly (with a javascript page for voting, which we could do with here!) so maybe I'm being unfair. But I can't help think that with better management of the groups there could be a lot more going on. It looks like a site that'll keep developing...