Ask HN: What is the value behind OpenSocial?

After reading through Opensocial's site and documentation, I find myself still confused. Perhaps part of it centers on the fact that I wasn't around when it launched.

Is it a failed attempt at making apps adopt a universal api? And I say failed because Twitter and Facebook aren't part of the movement. Or is it going to be a force to be reckoned with in the future? Also, how does it fit into the Wave's upcoming launch?