Or is there another party I don't know about? :P
[beta] : Actively participated in the private beta.
If I recall correctly from the Web Applications stackexchange beta, these are awarded just a bit after the site goes public beta, once you have actively participated.
This site has been running nye on 3 days. It's far, far to early for the beta badge to be awarded.
And now they're awarding the beta badge, after what seems like a very short private beta, at least I was notified that I had been awarded it as I logged in this morning. Presumably this means that the Private Beta is over and we're into Public Beta now.