I think most of us have been "caught" unknowingly by one means or another in this. I choose my words carefully. Would any sane person actually go to a stock photo site or Google and take an image with a watermark on it clearly showing it is copyright.
You'd be surprised: I've found some photographs from my online archive which have never been licensed to anyone pop up as infringements, where the only way the person could have gotten hold of them was to do a screen capture of the archive page.
I used to have my name appear as a 30% transparent watermark in the lower right corner of every image - the infringers would either use the shot with the watermark, or trim the image so as to remove it from the picture. Using the picture with the watermark in place destroys any claim that you didn't know it was a copyright work, as does any attempt to remove it.
These images are just floating around, no watermark id, for the unsuspecting to pick up, use and "get caught".
Horseshit.
I'm sorry, but the pre-purchase images that you can view on my archives now carry a nice, fat watermark in the center of the image to deter outright theft, but when someone licenses an image from me, it is quite rightly supplied to them without a watermark, and a byline credit will normally appear in some form of proximity to the image in question. Sometimes it's immediately beneath the shot, sometimes it's at the bottom of the article that the picture is used in - and sometimes, especially with select US clients, there's no byline at all (because the US does not have laws on the books regarding right of attribution)
Whenever a search engine such as Google indexes a web page, it will do so "as is", meaning it will link to both the source page, where you can see the shot used in context, and the image itself. So: When Google indexes my archive, it'll show the shots with the watermark in place; when it indexes a page where a client has legitimately licensed the shot, it will show it without a watermark.
Now here's where people fall foul of their own ignorance of the law:
a copyright work does not have to display a copyright notice to enjoy protection under law. It's not a legal requirement.
Claiming that an unwatermarked shot which you can
right-click, save as via Google is the equivalent of a fishing lure is akin to thinking that you can pick up a new ride by testing the doors of those sitting vacant in a car park and, when you find one that's unlocked and with the keys in the ignition, thinking "jackpot!"
There's a very simple rule to using images: if you didn't create it yourself, or if you didn't get permission / obtain a license for the use, then you
might be infringing. If you're happy to take that risk, then by equal measure you might also fall foul of the consequences of your choice.