I ended up offer $40 top anyone in my community if they showed me a receipt for new Nike shoes they'd purchased for themselves. This was a promotion for my business. I extended the offer to folks on 4chan. They just had to email me a picture of their receipt.
I caught on that people were doing Google image searches of receipts. I made an announcement that I was no longer honoring the deal because I was being taken advantage of. Then someone emailed me that he was getting together with other 4chan users that I refused to pay and they were going to sue.
Can they do that?
no, they have no legal grounds and they are trying to scare you
besides, the cost in legal fees is probably more than the $40 they'd get anyway