Everyone's favorite meeting organizer site that was oddly popular during the 2004 presidential campaign, Meetup.com is now charging for their service. While I think its nice that they get paid for their site, I really don't see them being that successful. Current members can just as easily go to their next meeting and grab email addresses from members and then use a gmail account to send updates and/or a blog page to keep members informed.
The only thing that will keep them afloat (assuming google or yahoo! doesn't introduce a free competitor) is if they have achieved the network effect of having them be the default place for online meeting organization. If they are the go to place when someone says 'Hey, we need to organize a meeting' then they will be okay. Similarly if they are the go to place when someone says 'Hey, I'm looking for a currently existing group of like-minded people to talk about my love of Gram Parsons' then they might be okay. Since I have a few groups that I belong to and they communicate to me via email and not meetup.com, I'm not optimistic.