I'd be careful about getting too vigilante and launching something that could be considered a denial of service attack. Once you start escalating, things can get nasty for everyone - just my opinion. For those wanting some kind of watermarking without paying Digimarc, JpegX is a freeware program that will hide text in a jpg image file with optional password protection. It's under export restriction, so don't download if you live in Cuba, Iran, Sudan, Iraq, Libya, North Korea, Syria or any other country considered to harbor evildoers. As an example, this image of old Harry (Geralday?) is the same size and looks the same as the original render but it contains the text of the Gettysburg Address. It's probably not as robust as Digimarc but if the rightclick save the file and post it as is, you would be able to retrieve whatever text you embedded and prove ownership. http://nerdlogic.org/jpegx/

"Democracy is a pathetic belief in the collective wisdom of individual ignorance." - H. L. Mencken