I don't like this move very much either. It's not the decision to sell it that's the problem, but the timing. The forums were created only a couple months ago. To not only change hands so soon, but profit from it, makes it seem like you're selling out. Ideally, the guy that bought it should be making a post alongside a trusted member of the staff, explaining what's going on.
Anyway, it's not like it was sold to a big corporation. The guy that bought it doesn't seem to be that bad. He already has at least one successful fourm and some other websites, although... I'm going to assume that this forum will become overloaded with ads as his other one is.
Also, why the switch of names? socialdiscussion sounds better, and if you want to pretend the name to be "join the discussion", people are going to go to jointhediscussion.com, instead of joindiscussion.com... just a thought.
Like OC, I think that I too may be bowing out of the discussion, sometime within the next few weeks and am now registered at ubuntuforums, so I hope that I'll be seeing many of the Socialdiscussion forumites over there too...