On why “Diablo III” isn’t an MMO:
Sams: When we’re deciding what type of game we’re going to make, we look at what the gameplay experience is going to be. We talked to the team a lot and say, “What is it you want to play? What is it that you want to make?” And we really felt like “Diablo” is a franchise that is very cooperative in the manner in which you play it. We felt like the gameplay experience that we had delivered historically with being in a non-persistent world was the right way to do it for this particular product. I think a lot of people expected us to say that this is going to be an MMO — maybe an obvious choice in a lot of people’s minds. But really, the bottom line is we thought the right game to make was “Diablo III” in the way that we’ve announced it.
That's not to say that it won't have multi-player via Battle.net, but that's not what makes an MMO, now is it? Check out the awesome interview to find a glimpse into why Blizzard is one of the most impressive game makers out there!