I don't think many people unaccept answers and pick a different one. Also, I think many people upvote the accepted answer just because it was accepted.
But I see a couple of silver badges (Guru, Englightened) that only apply to accepted answers, and it makes me wonder if that stops people from making further suggestions once a question has an accepted answer.
I guess I just wonder about which badges should really be sought after... perhaps badges for "first answer (with upvote from asker) on a question that's over 24 hours old", as a way of encouraging people to try to help out on older questions.
And more value placed on upvotes from the asker, rather than from peers.