A few years ago, I found a stock-photo house in Spain was selling this photo, found here on the site, without bothering to tell me (or pay me). After that incident, the stamp appeared. I got a lot of complaints, and in the past couple of months I had let many "bug-less" shots onto the web.
Sadly, my log robot noticed a recent upsurge in picture theft people using photos from botzilla on their own web pages (one even was from a site that was offering to sell the pix). And this one cropped-up in a German magazine last fall, and I still haven't been paid.
So while having a distracting rubber-stamp in unfun, being ripped off is even more unfun, and the stamps are back.