Note that the main argument Wolfire is making is that game marketplaces (buy/download the game) and game platforms (online features, mod distribution, social pages) need to be decoupled. By integrating the two, Steam is vertically integrating, amortizing the cost, and then forcing every other marketplace to bear the cost of a platform in their pricing.

If you bought a game and paid for platform services separately, then competition can better exist for both of those roles. Which is good for consumers.