Foursquare, the location-based social networking service, now has its own holiday: Foursquare Day. It's the brainchild of Tampa resident Nate Bonilla-Warford and it started as a humble idea that in the past few weeks has exploded into an internationally-celebrated event for Foursquare's boosters and participating businesses. I'm at the Hyatt Regency hotel in downtown Tampa, host […]