You have to play online, though you can choose to play solo while online. In a few of those I am with people. The beta is VERY small only about an hour of play time though its repeatable. It's more then enough time to decide what kind of class you want to play ect..
Article came through my streams yesterday morning detailed how the Korean Rating Board was targeting the auction house component of D3 as gambling, which is outlawed. Korea is Blizzard's largest target audience, and it was thought that it would be delayed in order to maintain their goal of a worldwide release date.
Instead, in order to maintain their release goal, Blizzard flipped the bird to Korea and is going to nerf the hell out of their version of the game and strip the auction house (at least the real-world $$ part of it) from the game. I assume they will look for approval later on.
Approval Blurb (there's a billion of them on the net):
And what I was saying was they have repeatedly said the Korean issues is NOT holding the game back, that it's just not ready yet. Also I get all my info from http://diablo.incgamers.com/page/1, which I check daily.
It's pretty awesome. The content we are playing, over and over, in beta is watered down newbie started stuff. Once you get farther in it's suppose to be really challenging and fun.