Interesting thread - I assumed this would be here and it was!
How about another scenario (or two):
The $250 airline credit - seeing as how this is automatically deducted - should I only bill a customer the net cost of a flight? I think that the $250 is mine, and I would happily apply it to a personal flight if I had the choice, but I don't. I don't feel guilty or unethical about this one at all.
Another similar scenario - I have a Ritz card with a $300 travel credit. I was recently forced to change a flight (customer requested - "as long as the change fee is ridiculous... $500+ in their words). Supposedly change fees are allowed with the Ritz card, but not sure if this is considered one of the triggers for automatic reimbursement.
But if they have agreed to the change, and I'm paying my AF on that card for this type of benefit - I don't think I have an issue with this either. This will not cover the cost of my AF or even burn through the $300. If I had a choice to save this for a personal flight, I don't think I would because I wouldn't be in a situation (typically) to need to change the flight like I would for business flights. I admit, I'm a little more un-easy about this one, but don't think I'll lose any sleep at night.