Brand advertising has already been done in the MMO sphere. Anarchy Online's Free Play program has been showing users in-game advertisements for real-world products on in-game billboards since World of Warcraft launched in 2004. MMOs have survived since. Case closed.
Oh, you wanted more discussion. I see. It's been done before! Finally, we have some real precedent to talk about. Oh FunCom, you've finally managed to not disappoint me. Advertising models were one of the first types of campaigns to be applied to free-to-play versions of massively multiplayers that didn't hit perfection under a subscription model. In 2004, there were a tremendous number of MMOs to play, and people usually just stayed loyal to one. The fight for your subscription dollars was on.
Anarchy Online's Free Play program debuted in December 2004, just after the launch of the unknown but best-selling indie hit World of Warcraft, giving players a chance to play the game and its first expansion pack free of charge. Players subscribed to the Free Play game client would see advertisments in cities, towns, and other highly populated places in game for real-life goods, services, and companies. Advertising dollars paid for the game, as well as subscribers' choosing to pay and see fictional ads instead.