diablo is no singleplayer game. it's coop multiplayer with the ability to also do stuff alone.
and RMAH.
and anti-cheating because of RMAH.
and anti-piracy in general.
that's why it is online only. get over it. don't like it? don't play it. or don't buy it in the first place. simple as that, is it?
and someone who is playing on release day and claims to not have known this fact for quite a time before, it either lying, trolling, plain stupid or any combination of that.