I don't personally see what the fuss is all about. If people want to put watermarks on their photos, it's their prerogative to do so since it's their photo. If they want to put black boxes or mosaic over the eyes of their models, it's their prerogative to do so since it's their photo. If they want to post a completely blacked-out photo for comments, it's their prerogative to do so since it's their photo. Off the top of my head, I can think of any number of reasons why a watermark emblazoned right across the subject would be useful - it prevents leeches from ripping and posting onto a perverted website, or from using stock photos without paying, or from exploiting for commercial gain a model's photo without licence. It's not really that difficult to crop away a watermark or credit along the frame of a photo, but it really isn't much point for the potential leech to crop away the face of a model, or to slowly clone back the salient features. A lot of the guys and girls in here post up pictures of people without model releases, or with limited releases, and open themselves up to liability from leeches grabbing the same. Why shouldn't they be entitled to take whatever means they feel are necessary to protect themselves and their property?
At the end of the day, if somebody posts a picture for comments, give them the comments the picture deserves, for example, "Gee, nice picture, good framing, colors just right, a pity your watermark right across her boobs are distracting." Or, of course, everybody could just shoot film like I do, and run the risk of a really boring photo forum.
Just my 2-cents worth: everybody seems to be bashing on about self-righteous artistic purity while not really taking the copyright problem seriously.