Android and OpenSocial were platforms, and needed to attract developers to realize their full potential. Google leverages user data to improve their searches (and most of their other products), but there's not really a network effect in play: more users do not necessarily create a better user experience.

But with platforms, there's a real question of the chicken and the egg, and you have no choice but to drum up as much excitement you can, the earlier the better. Without the artificial momentum, it might not go anywhere.