Well I suppose I asked here because I knew that I share the same (very specific) interests as other YCers. Other people at Meetup may not necessarily even know about YC or Paul Graham or any of the other things we as a group tend to find interesting/cool.
meetup.com won't cut it. There should be something like a cross between meetup.com and flashmob.com and provide widgets for meet-up groups to relevant sites...