Nothing material is lost, but if you’re charging to see said piece of artwork and that dude who saved it on his computer shows it to other people you’re loosing money. And don’t come with the excuse that if they’re weren’t going to pay for it in the first place you don’t loose money, because that some cheap argument to get something free, i would like to see entering a store and grabbing a book and reading it completely, then saying that you weren’t meaning to pay in the first place so the author didn’t loose any money, they will kick you out inmediatly.