Proving you can indeed sell ads to a paid subscription game, Brandweek reports that World of Warcraft has sold an extensive sponsorship to Mountain Dew. Last summer the soft drink experimented with web 2.0 marketing, so if you're trying to sell ads to a 'cutting edge brand' in your niche, try surfing at Facebook brand fan pages.The sponsorship includes a 14-day free trial of the game online. This is a classic type of subscription site sponsorship that I first saw on The Economist's site several ...