We have had some people doing something similar in our industry. I set up at various coin and collectibles conventions throughout the year. Basically what certain people would do is ask to see an item in your showcase, get a price from you and then take a couple pictures of it. After they leave your booth, they would list the item on eBay for more than your asking price. If the item sold, then they would come back to your booth and try to purchase the item (sometimes even try to beat you down on the price).

Long story short, I no longer let people take pictures of anything unless it’s somebody I know.
Not sure what you can do to stop people from using your photos on a CL advertisement though?

Also, if I figure out that somebody has done this I won’t sell them the item. Let them sort it out with eBay and their buyer (not my problem).

If you’re going to be selling something that belongs to someone else, then it needs to be on an agreed upon consignment basis, not shady stuff like this.

What happens when a Pinside member sends the seller funds for a machine he does not possess or own and then goes back to find the real owner has already sold it, doesn’t want to sell it anymore or refuses to sell it?

The problem is the person making these sort of advertisements has no real authority or control of the actual machine.