When I was a child, I thought I was clever because of things I got away with. At some point I got older, and with some reflection (as well as observing young ones thinking they are getting away with things), I realize that the adults in charge of me probably knew what I was doing, for the most part.
I feel this way about raiders who try to manipulate loot systems. They may think they are being sneaky trying to justify a sidegrade into not paying for it, but the officers are watching. Just because no one calls it, doesn't being it wasn't noted, every time it happens, for weeks.
And if, by chance, that raider decides to start bragging about their exploits, that's when the party is over and the sidegrade option gets removed. If no one wants to pay, it gets melted.
Instead of saying that the raider has ruined it for everyone (it hasn't ruined the system for folks who only take what they truly need), I would just like to say this:
Are you so bad that you have to cheat at World of Warcraft?