what's with these ppl selling oz retail w/ receipt items that are under a month old claiming they decided to move to other (brand/format/country)?

just now I saw this ad for a 1wk old 5D2 cuz the owner decide to move to MF. Seriously?
But there are so many ads for stuff about 1-2mth old with some weird claim. Initially I thought it was Canon staff using their 40% staff discount to rort the company, but many of these have retail receipts so I guess not?