I noticed very often in stack overflow that questions aren't marked as answered, simply because the author of the question became inactive, does not log in to SO very often or simply does not care to mark one of the answers as accepted.
Note that only the author of the question can currently mark an accepted answer, so there is no way to change this if someone does not log in to his account any more.
I think it would be useful when searching for a topic, finding the answer which is most likely the right one very quickly.
My suggestion is to create another review category after x weeks of inactivity (i.e. no more comments added, no more answers created, no changes whatsoever), for example "Unaccepted answers" and let the SO users review this allowing them to mark the most suitable answer (say, if they have 2000 reputation points or more).
Of course, the author of a question should be notified so he has the chance to mark the right answer by himself before that happens (giving him a grace period of x weeks before the question is put into the review category).
Is it possible to add this feature to SO?
I originally asked for automatically select an answer, but that topic is already covered here as Thomas told me, so I have changed my question.