That's a risk I hadn't considered for nostr marketplaces. Interesting. In theory, because of its open nature, we could end up with hundreds of sites being set up specifically to catch people out. It'd certainly put people off. In my site I've implemented a simple send message to seller system when you've found a product you like. The way I see it is this is more like Facebook marketplace. The relationship between buyer and seller matters. I do wonder now how automated shopping systems will operate longer term. In fact, I wonder if they should, except for digital products.