Foursquare (https://foursquare.com/) is a marketing service for local businesses, helping them to target potential customers with special promotions, particularly, with promotions based on where the person is walking or driving at the moment. When the customer (who has registered with Foursquare) is walking (or driving) down the street in front of the restaurant, they get a coupon for immediate use in the restaurant, for example. This is a powerful marketing tool– if the business knows how to capitalize on it. Foursquare is a major advertising site, with over 20 million end users and over... [...]