Two viewpoints on this. First, if people are doing work and receiving payment, they need to declare that and pay taxes just like the rest of us. And I have a long history of 1098 income, so I am familiar with this. Second, it is a bit nosey to get into what personal items we buy and sell. None of their business.
Oh, that's telling 'em off! I bet that the IRS feels really crushed when people tell them that they are being "a bit nosey!"
Leads them to crawl into a corner, and sorrowfully review the moral principles of their activities!
Regards,