I don't think you're using the term correctly. All the other stuff in this thread aside, the phrase "sense of entitlement" is typically applied to those who want to appropriate from others, not to those who want to keep what they have. No matter how boorish the folks here seem to you as they speculate on what they might do in a hypothetical situation, you can't accuse them of having a sense of entitlement for choosing to keep the seat assigned to them. If anyone has a sense of entitlement in this situation, it's the person who believes he is entitled to another person's seat.
You may believe he is entitled to the other person's seat too, but please don't accuse the person sitting there, who bought that seat and wants to keep it, of having a "sense of entitlement." No matter how noble the motives of the appropriator, or how base the motives of the possessor, the phrase "sense of entitlement" can apply only to the person who wants to take from another, not to the person who wants to keep what is his.
You MAY be correct from a strict semantics point of view, but I would be very surprised if most readers of this thread did not understand the point I was trying to make.
I also don't necessarily agree with your strict interpretation of this term. One could easily argue that someone has a sense of entitlement in that they feel they are entitled to not have to think about the needs of others. Clearly this discussion on semantics can go on for a long time and not come to any meaningful conclusion.
Clearly, the point we've been discussing has more to do with whether or not a seat switch should happen to accomodate (to whatever degree) a family with a disabled child. I am still more than a little dismayed to see how many FTers feel that this isn't a 'no brainer'.