i hate to be simplistic about this, but I'm not sure why anyone would be against multi-player.
i mean, if you dont like it - dont use it. and yes, you could make arguments about it taking resources from other development - but that's a tricky claim. when a company decides to serious expand their offering in such area (and one that presumably would expand the reach of the game and make them more money)they will simply hire more staff. the person who writes the quests isn't going to be writing multi-player code...
I'm not a big fan of multi-player in my CRPGs, but if it will sell more copies and reward Larian with mucho gold - then they should go fo it. Meanwhile, I will probably stay in my happy single player land.
