Say you want to move sentiment around some idea. If you can manipulate the volume and direction of sentiment around that idea, say by green lighting a targeted segment of known dummy traffic (sock puppets, whatever), promoting certain posts above others, etc, you could potentially achieve that goal.

I think twitter, like others in its genre, has potential as a interface for mass manipulation or enchantment, and anyone who would "own" it outright, in its current form, is likely dangerous.