Ironically enough I saw this via stephen frys twitter - but it seems to not be mentioned in the forums here yet and I expect that here would be a ideal place for it to spread for those that dont follow the blogs on here.
http://www.geekzone.co.nz/juha/6247
http://creativefreedom.org.nz/blackout.html
So anyway, go get the black image or make your own and put it everywhere you can, I have done bebo, facebook, nzdating, wordpress.com, and some others that escape me sofar.