So, seems like anyone can log in to the D3 beta at the moment. Download the client etc and enjoy while it lasts!
Official battle.net forums already got hang of it, no official blue announcement about anything.. Could be a bug, or a "secret" stresstest?
Enjoy while it lasts!
Not sure if this is bannable offense to these forums, since I'm not sure is it a unintented bug or just a stresstest which they didn't announce yet.