If somebody used my photos I’d be chuffed to bits, I’m a hobbyist underwater photographer and if one of my photos made it to print that would be payment enough. However if I was a professional and relied on my work paying my bills I agree initially, but then I would be posting them on professional sites not open internet forums. If you don’t want to share something then you should make that clear by using a watermark or similar as you say. So I guess I can see both sides of the points that have been made

Please browse my photos and enjoy.