The #1 group on Meetup right now?
most chapters in most cities with most members, most active?

STAY AT HOME MOMS.
They are missing infrastructure so they are reinventing it using these tools.

If you want to know what technology is going to change the world, don't pay attention to 13-year-old boys, pay attention to young mothers because have got not an ounce of support for technology that doesn't materially make their lives better. [Meetup] is so much more important than X Box but its a lot less glitzy.

-clay shirky http://www.youtube.com/watch?v=sPQViNNOAkw&feature=related