nautical, I'd have agreed with you more 40 years ago but things have changed.
"when you add a copyright
symbol or otherwise say they are copyright
, there is little room for doubt the infringement was intentional," Since the US became a Berne Convention signatory in the 70s, the law clearly says it is no longer necessary to indicate copyright. On the contrary, ALL work is presumed to be copyrighted UNLESS there is a disclaimer elsewise.
The only advantage to placing a copyright slug on the work, is that someone can say "Well, I tried to find the artist but there are 5000 "John Smith"s out there and I couldn't find the owner." That's still no excuse, although it might be taken as a mitigating circumstance IF they could prove they'd made some real attempts. Putting your name on the image, makes it more likely that someone can contact you.
Watermarks? Come on, no one actually needs to put a VISIBLE watermark across the image these days. There are technologies that put a totally INvisible watermark in the image, and then go out and search the web for images
that have that mark embedded in them. These are all based in steganography, which has become a big business (and big encryption problem wrt espionage and terrorism) in the past decade. Steganography works, very easily and effectively, and any script kiddie can use it to invisibly watermark any image.
Most folks overcomplicate the issues around copyright, but the laws are fairly simple, the explanatory materials fairly good, and there's a HUGE amount of case law to clear up any questions that people have. Anyone planning to sell images
(or simply protect them) needs to do a little research
and come up to speed on that, the same way that someone opening a burger shack needs to find out the correct temperature to cook and store food