personally, i am keeping a very close eye on the
diaspora* projet : it should be coming in the next few months and will be like facebook, only with privacy.
as for social media as a marketing tool... i just came across this pertinent video :
i think facebook is shooting itself in the foot and every other part it can reach and couldn't have managed it better if it had deliberately wanted to die, and i really have to wonder about the guys running it. a lot of people i know are leaving it (inasmuch as you *can* leave it... they make it nearly impossible to delete your account, you really have to work at it) and i never post anything even remotely personal on there.
as soon as diaspora launches i'm planning to go there and try to convince my entire network to come with me.
however i think facebook still has value as a marketing tool, as has been mentioned by others, and i probably won't delete my account for that reason alone.