This isn't really a technical question... I'm mostly kicking off a conversation....
How do you build a community with Drupal? Here are some of the ideas I am coming up with.
1) Have it easy for people to log in with their existing accounts (Facebook/Twitter etc)
1a) Fetch their icon photos from Facebook
2) Have people "follow" others with the same interests
3) Have an extensive User Profile system
4) Have a private messaging system
5) Also post to Facebook and Twitter to help piggy back off users' communities on those systems....
6) use people's avatar icons whenever possible - not just their names.
7) Try to get things live (like Facebook or Twitter page updating every few seconds - not just on refresh)
What do you feel is needed for an online community? What have I missed?