I would have preferred single-player as well. Single-player makes me feel more in control of the game. Also, I somehow doubt that even Bioware can make an MMO with a story as good as some single-player RPGs. And to keep an MMORPG going they'll have to keep the conflict going without resolution, which is one of the key elements of a story. They won't be able to make the Jedi or the Sith win the conflict or they'd make all the players of that faction mad.
This is one game I'm not looking forward to. MMO's just ain't mah thang.