I wonder what this means for Soldsie, the service that allows users to buy within the comments section. Seems like the best UX should ultimately win and that puts Facebook at a big advantage.
Unfortunately that's always a risk when you develop for FB or any platform. If it is bad for users (like most of the Zynga notifications were) or something they want to pursue themselves (like birthday gifting), then bad luck. You get the advantage of their distribution at the cost of platform risk.