So I'm currently running close to 50:50 with unaccepted answers, which is a little demotivating; Furthermore, discouraging. If I search for something on SO and don't see an accepted answer it rarely pays off clicking the question - but often it might.
How about a stack that can be viewed of month old questions that have answers but haven't been accepted? People could confirm/deny these as appropriate and a message could be sent to the question asker as to why they haven't accepted. If they contest, we know the answer is invalid and the questioners accept rate can be adjusted appropriately. If they don't reply within a week and someone else confirms the answer, points are awarded and the question closed.