Radio Shack was scheduled to end a month-long Foursquare promotion yesterday, but instead has chosen to extend the campaign through June. Why is a major national retail chain so smitten with their Foursquare initiative, and has it produced measurable success? At the Ad Age Digital Conference last week, Radio Shack CMO Lee Applbaum said that Foursquare users at Radio Shack were generally spending 3.5 times more than non-Foursquare users. Read →