Everyone is checking themselves in, but this is hardly rehab; it’s Social Media Week in New York City.  On Foursquare, Gowalla, and now even on Yelp, people are sharing where they are and vying to become the “Mayor” of venues they frequent. They say that all news is local, but instead this is Where word-of-mouth, real-time, and overshare intersect. Location-based social media have become the next-big-thing as opinion leaders look for new ways share their influence.  Over the last year Twitter has cemented our collective desire to share what we’re doing, who we’re with, and increasingly where we’re doing it....