Agree Kingair,
Why not take it one stage further and hand out the overwing instruction cards and say that you will return in 5 mins to ask a question about the exit to make sure they fully understand. I'm sure many will then pay particular attention to whats written on the card. If they can't answer the question then they get moved to a non-emergency exit seat.
My main beef is those regular travellers who think they know it all. Even if you do, PLEASE PLEASE pay attention. Its amazing to watch the affect that a newspaper or a sleeping passenger has on the attention of the surrounding passengers. They subconsciously think 'well if they aren't paying attention then I don't need to either'. For those regular flyers that do know the exits and emergency procedures; it won't help you if the other people around you don't know what to do and end up blocking your path. In an accident we all know time is critical. Two seconds could cost you your life. Now tell me your happy that others around you aren't paying attention during the briefing!
How sure are you that passengers in your vicinity know where and what they should do in an emergency?