A lot of what John says is true, it's difficult to have events in everyone's backyard. With our terrible traffic, its difficult to find locations that 'most' would consider 'central'; hell, its difficult to get anyone in MD/VA to cross the Potomac to the other state for fear of the unknown LOL
All of our Thursday socials are hosted by volunteers who live in those areas since they are the one who needs to find the location, pay the bill, run the event, and plan all aspects of it. Believe it or not, its not easy to find a location to host us. One of the main things we require is a good parking area; goes without saying since we spend a good part of the evening hanging out with our cars. I've stayed away from anyplace that only has street parking, paid parking, and lots that aren't at least half empty after 6pm.
Perhaps the biggest hurdle we face is finding a place that can handle our 'shot in the dark' headcount. The first question they always ask me is 'how many people?' My answer is almost always, 'pick a number between 2 and 50'. Its very difficult to get an idea of how many people will attend no matter how many times we ask people to RSVP; it's been that way for 6+ years now and I doubt it'll change.
A few years ago, there were some people who thought DC would be a good place to host a location until their research led them to conclude otherwise. Most people want to get the out of the city after work and not across town. They looked at a few spots in Chevy Chase, but again lack of parking was a big issue. Maybe there are locations now that may warrent another look, so if you have any, check them out and report back what you find.