Originally posted by rawr Watermarks can be legally useful even if they may technically be easy to 'crack'.
If you can demonstrate that the original was watermarked, but the offending party took deliberate steps to remove the watermark [even better if removing the watermark was not technically easy to do], it may add strength to any claim for damages and/or copyright infringement.
How do you plan to do that? If they can algorithmically lift the entire watermark now (as shown in the article linked in the original post), leaving absolutely no trace, you'd have no proof. Unless you filed it officially. Otherwise it becomes a sticky legal case of showing you hosted the image before they did, but even that can be thwarted. The thief could strip your watermarks, watermark your image as theirs, back date the image and the upload date earlier than yours, and host it on their own site. Or you prove you were at that setting at that day and time of the photo and they weren't. But that's annoying to have to do.
I find better options would be to keep the image size relatively small (I use 1024 or 1200 on the long edge) and watermark multiple places with different watermark designs. For instance, have the general 'obvious' watermark but then have a smaller one along the edge of the subject or a part of the scene and another in the background with less opacity. Complexity in the watermarking.
Then again if we really want to be sure, as Adam alludes to, just don't host the image online!