If you're selling exactly what everyone else is selling the competitive point is customer service and price--I'd worry much more about that than someone copying your image. Such stores generally use the manufacturer's images anyways.
Did I say otherwise?
> why would you invest a ton of money into quality photography and then cover it up with a watermark?
To make sure that this quality photography stays as a competitive asset or if used by others, turns into advertising for my store.
> If you're selling exactly what everyone else is selling the competitive point is customer service and price
When you're selling something online, photography is most certainly a differentiator. It is also a substantial barrier to entry for the competition, because quality photography is difficult and expensive.
> Such stores generally use the manufacturer's images anyways.
Manufacturer images, when they exist, are almost always terrible. Having good photos to clearly show off the product and everything included is the difference between a buyer clicking BUY and having them wander off.
As opposed to those analog watermarks that we've all be hand-applying to our JPEGs? :)
http://images.google.com/search?tbm=isch&q=watermarked+image...
Regardless, you seem to have missed the gentle humour in my original post.
I can't speak to Google Shopping, but Amazon requires a high-quality image before you can list a product. So if you spend money on the shot you don't want others stealing it. EXIF data and other non-watermark solutions are easily removed.