Single player is online?

There is offline single player, but it's something we're going to attempt to discourage as best as possible.

A lot of us, myself included, and probably a lot of you and your friends had the exact same Diablo II experience. You get the game, start playing, your friend says let's try co-op, and when you log in your characters aren't there. After a slight freakout moment and potentially some use of Webcrawler to search the World Wide Web with Netscape 6, you realized or figured out that you had to start over. That's actually an experience that can cause someone to stop playing the game. Maybe you or I let out a huge sigh, and maybe a brief mourning period after realizing the last 60 hours were completely wasted, but we pressed on. That's not the case for everyone. Maybe most people. I actually refused to start over for a while and continued on in single-player before finally jumping on Battle.net. Who knows what a lesser man would have done... ;)

So, if we can get people online and creating character on Battle.net from the get-go, there's less chance of that catastrophe. But there's still a play offline option, if you should need it.

Q u o t e:
I myself never had an issues with not understanding my single-player character was single-player only, just like I never had any trouble understanding what happened to my weapons when I hit the weapon-swap button. I guess I'm just smarter than your average bear? o_0

Let's go with that and do the thing we're going to do and whenever you see the play offline button you can giggle at how you don't need to have it way off to the side there.