Cordelli, I disagree with your comment,

"I'm sure a sampling on the street of people without a vested interest would give much different results."

If you replace upgrade with some generic, but earned perk, I'm sure that the answers would be similar. Most people in the civilized world are willing to work within the boundaries we create for ourselves, "Laws". The more we do this the more civilized we become by definition. Perhaps this tread suggests that we are in fact civilized and not just a bunch of "upgrade me now for free or I'll never fly your airline again!!" fanatics. Or, maybe not.