So, seems like anyone can log in to the D3 beta at the moment. Download the client etc and enjoy while it lasts!
http://eu.battle.net/d3/en/forum/topic/3724212521
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.