It felt like these apps had found a hack that was taking advantage of the platform, but really this was just the result of the platform being poorly designed itself. The selling point for developers who picked up on it was, "You can make everyone who uses you spam all of their Facebook friends." Unfortunately spam, especially when it's coming from your friends, works like a charm. Facebook eventually had to stop allowing that before it let itself turn into a MySpace filled with little widgets.
Facebook's real problem wasn't just that it wanted to own everything itself, but that it didn't build the platform the right way in the first place.