If they don't want it hotlinked, the web designer can make it so it doesn't.
Usually that doesn't stop copying and pasting the URL, but it will prevent image hotlinking (and is amusing because for the person doing the linking, the image is still cached so they have no idea that everyone else is seeing the "stop being a cheap *******" gif that the originating website has set up for hotlinks.
At the same token, the idea of "if it's online it's fair game" is flawed, because that will only encourage people to not put things online. And then where would you be? Sad and unable to view images, that's where.