Another reason I have for not feeling bad for refusing to give up a good seat is this: if I were in the couple's shoes (getting an upgrade at the last minute), and the gate agent told me there were no contiguous seats, I would decline the upgrade (if contiguous seats were available in coach). If the agent volunteered to board the plane and ask people to changes seats, I wouldn't stop him/her. But I wouldn't board the aircraft and try to do this myself (especially in First), knowing that seats are always assigned before you board the plane (except Southwest, but then there's no First Class, either).

My opinion on this is that when you're flying with someone, it should not be a big deal to choose between contiguous coach seats or separated first class seats.

To generalize, why should it be that when person A asks person B to accept an inferior situation in order to please person A, person B should be made to feel obligated to help out person A? In other words, the very last person to ask for an exchange (due to good planning) should get bottom of the barrel?