As stated the photog owns the copyright and the image. It does not matter how they display it or where. No one has any legal right to do anything with it unless they have the permission of the photographer/copyright holder.Yeah I caught that earlier. Haha
What about a photo with no water mark? Is that OK to post on social media?
For instance there is a thread here with a guy posting photos of vehicles at the Rage. He does not seem to be selling them and they have no water mark. Would you take that as they can be used or still no?
Think of a fruit stand, there is lots of fruit displayed on the street, but you cannot have any of it unless you pay for it or the guy running the stand gives it to you.
Its very very easy to avoid problems when you want to use a photo for anything. Ask the photographer first.