If I were going to describe this to a friend, I'd probably say "like flickr, but for data"... not something you can put in marketing materials, I know.
I'd like to abuse this reply to ask that when you add tools for geodata, that you please please please do what you can to help people produce visualizations and rankings that are not horribly skewed by poor choices of geographic boundaries.
I know this is a hard problem, but for people who don't do this all the time, it's really easy to end up with a headline like "Manhattan Leads the City in Pedestrian Deaths Per Square Mile, Study Finds" (Manhattan is, of course, the densest borough in New York City, so this probably isn't terribly useful information). I've seen maps that might show, for example, the areas of the US with the highest number of coffee shops per square mile, but the map is done based on counties, so here in Seattle we end up not looking terribly dense since over half of gigantic King County is mountainous and unpopulated.