It occured to me a few days ago that you could probably build some sort of decentralized ecommerce on Nostr. Sellers would send sell-offer events to relays and buyers would see those and use encrypted DMs to make buy-offers. When an item is sold, the seller sends an event to delete their sell-offer.

I have seen Nostr events that mention RoboSats offers, but I haven't looked into what those are or what they mean.