Amid the unending din of posts, tweets and articles about South by Southwest Interactive, one thing became clear: mobile location apps are the next big thing. In one corner was Austin-based Gowalla, fighting on its own home turf. In the other was Foursquare, the NYC-based startup that many associate with the ‘check-in’ craze. But regardless of who wins, unless services like these open up their data, we all lose….