Very cool. I haven't looked at what Meetup has available for an API but I've rarely ever seen its data used as a way to find out about a city, even though it's a great way to (manually) look up interests. You'd miss out on things that are on Eventbrite (but no reason why you couldn't combine their data...), but otherwise, it seems like a solid way to at least find hotspots for interests, particularly regional cities (i.e. not New York/SF/Chicago) that have, for whatever reason, an especially strong group.