@Jane - Meetup.com is expensive for just meeting up but the site has everything we (North East Ohio Meetup) needs to conduct our meetups. On our first meeting, we had a discussion on whether to user a WordPress site with custom domain to have for our meetings or use Meetup.com. We decided to go with Meetup because the WordPress site would be just another site that needed maintenance, would need some sort of kick ass events calendar which is something that is still lacking overall in the plugin community, and it would be difficult to spread the word regarding our meetup group when people go to Meetup.com and use their zip code to see if anything is near them.

In our case, WordPress just wasn't the best tool for the job. As for the data, that data really isn't important.

@JTPratt Media - Meetup.com has been around for awhile and it's how I discovered relevant meetups in my area. It's also a cool site and has much of what we needed to get out group underway. After we registered our group, we immediately began to gain members from the local area. This would have been hard to do with a brand new WordPress site. They have so many people creating WordPress meetups that they dedicated an entire sub domain to it.