BuddyPress.org

The stuff like posting pictures of your newest pet or latest vacation – that “personal interest” and “personal interaction” stuff that makes people warm and fuzzy and feel like they belong to a group/community.

Precisely. Anyone who’s been running web communities for any length of time knows how absolutely important this kind of thing is to people. A community without it, unless it’s grounded offline in some real-world way, will die. And it happens in forum-style discussion threads.