Well, it's good to know that there are some people out there with enough self honesty to think about this issue.
I must confess: when I signed up for my affinity card I was given the standard bonus two months in a row. If they ever notice the error, they can take the miles back with no protests from me. I'm sure that there have been plenty of times in my life where I have paid too much w/out realizing it. I'm not trying to thwart morality with that rationalization, I'm just appreciative of any random windfalls that come my way.