I've always wondered why Etsy doesn't prevent people from doing this by getting rid of the right click option. I've seen websites before where if you try to right click on an image to copy or save it, it will say, "opps!" or something like that, and not allow you to do it. I talked to my husband a little about it (he's a web designer), and he said they should be able to make that happen across the site.
Sure...people could still take a screen shot, but there are a lot of people who don't know about that feature, and there are computers that don't have it.