I would assume the same is true for any niche... making it much more advantageous for a plane owner to use a friend's account who has actually sold aviation related stuff before on ebay.
Maybe. . .but I don't know many people selling multiple planes on eBay. Save for dealers, who are out to move stuff they can't sell locally. Which, to me, is suspect anyway.
When I was an FBO rat, I remember it was generally accepted that one should NEVER buy an airplane on eBay. Good aircraft for decent prices always sell well, if not locally, then on Barnstormers or Controller. Maybe Trade a Plane.
The eBay sale was like a last resort to get a buyer who was naive enough to buy without inspecting first. Or one who would bid, then come out to see it and at that point would have so much invested already as to not want to back out.
The "selling for a friend" bit has always seemed to be a clever ploy to gain some plausible deniability for the seller. Ecce: "Damage history? Well, it isn't my plane so I can't really say." Or "My buddy has never mentioned any damage, so I think it's clean."
Plenty of good deals out there on airplanes, if you're in the market. And if you're that cheap/poor that you need to pay absolutley the lowest bid price possible for your ship, airplane ownership is probably not for you.
These guys bought on eBay. . .