What's the point of seats being there then?
Hey it's pretty simple really. You have seats next to an emergency exit. Ideally you want people sitting there who can help in an emergency. First priority would be travelling airline staff who are specifically trained for such emergencies, second priority would be to those who are fit and able-bodied, lowest on the list would be other less able-bodied people.
So, don't be supprised to see airline staff occupying exit seats. Also, if you want an exit seat then you'd better make sure you check in before anyone else who also wants an exit seat.
As for tall people, there is one other option that hasn't been mentioned yet. Get an isle seat and hang your legs out into the isle. Sure it'll be a pain moving them every time someone wants to move through the isle, but it'll be better than the other seats.