As a journalist who was once personally hit by false accusations regarding award fraud, I did some research on this issue a few years ago, at a time when SWUs were still all paper (like UA's current SWUs for use on LH metal, which appearantly are still a eBay and mileage brokers' favorite).

Two points to seperate fact from myth:

1) eBay auctions are often conducted by professional award brokers, so the eBay seller is often NOT the guy who's name is on the SWU. In these cases, neither the seller or the buyer are violating any rules, but the guy whose name is on the SWU is. If UA finds out about that name (e.g. by test-buying the auction), the accountholder will be in trouble.

2) My research showed that the really big players in the SWU fraud scheme weren't 1K MP members but UA associates who had access and means to print their own stacks of vouchers or employees who "recycled" heaps of vouchers they collected at the gate from upgrading pax by not turning in those vouchers and reselling them instead. This isn't speculation, there's solid proof: For example, a mileage broker I interviewed once bought several vouchers that he had already sold and used previously in that very year! Since this broker made and kept copies of every voucher that went over his desk, these vouchers were clearly identifyable as "recycled". So UA staff definitely was (and maybe still is, I don't know) involved in fraudulent acts regading voucher sales on eBay. Imagine the poor 1Ks whose vouchers were recycled that way: When caught, they lost their accounts or were punished otherwise (because it was THEIR name on the voucher), yet they didn't do anything wrong. They didn't even know what hit them. Now, that's immoral, innit?