I do.....
The DEAL was one $20 giftcard for $10. He decided to try and exploit the system thinking he could buy multiple but the deal was for only one. They said, "hummm, well it is only 1 per person, so he must want to purchase many more for the normal price" and that is what they got.
For your bread analogy... If there was a deal on the bread at safeway that was $1 for first loaf, limited to 1 per person, and they decided to buy 10 loaves of bread thinking they would get them all for $1 each. Yes, I would expect their card to be charged $1 for one loaf and the normal price for each additional loaf.
I guess the lesson would be, dont be a greedy prick and try to make money off a generous deal and screw over future deals.
To be honest, I doubt they are really going to charge said person $21 for the multiple copies. I am sure they will just get canceled. I mean, doing that probably is not legal. I dont see how any credit card company would allow someone to get stuck like that.