Doesn't matter. Personal resposibility. I'm not ok with the rationale that when stupid people do stupid people things, the rest of us get to pay for it. There's way too many stupid people for that theory to even remotely be acceptable.
I'm betting the ones causing the problems can be found out and IP banned in very short time.
Send them an email stating its been determined they are selling in quantities that would require a dealer/vendor account. Offer them the account, lay out the costs and tell them either become a dealer, or your exchange posting privileges are now reduced to X per month or whatever, or you cannot post in the exchange at all but can contribute to the other forums. Make them make a choice and take responsibility; don't bring their bullshit over to the rest of us.
Just from cruising the exchange, I can find 3 or 4 right off the bat that I'm betting would 'qualify', and I'm not even trying to find them.
You’re still suggesting Frank and company do free work.