What do they do for almost-white images? Hopefully at some threshold they switch to black test. Even at that, a black/white tiled checkerboard image would leave the url illegible. They should have outlined the white text in black.
Also, it looks fairly easy for an "unfair use"-er to "heal" the watermark away. They should consider a watermark with higher entropy. (like a stipple-shaded box or one with subtle random variation in shade around the box edge.)
Also, it looks fairly easy for an "unfair use"-er to "heal" the watermark away. They should consider a watermark with higher entropy. (like a stipple-shaded box or one with subtle random variation in shade around the box edge.)