well, they are developing quite a bit, but they test out the features among subsets of their user base long before the features are available to everyone. And in most cases they probably turn out to not be as good as they seemed they would be, and are tabled. They are pretty careful about changing things... I mean, if it ain't broke.

Personally I prefer it far, far more than the constant changes some startups seem to feel is necessary to justify their existence.