[Editor's Note: A look at special offers on location-based services.] Christopher Heine - ClickZ - 8/13/10 For the last several months, big brands have been consistently unveiling special offers on location-based services like Foursquare, Gowalla, Loopt, Booyah, and others. We’ve seen percentage-based discounts on purchases, dollars off, restaurant loss-leaders like appetizers and drinks, and sometimes even free meals. ...