tineye.com is a better way to look for your images that have been used elsewhere online.
My point was: if you where to start producing images that were of higher commercial value to 'others' - then your point of view may change rather quickly - or maybe that should read: it would need to change rather quickly - because otherwise, you probably won't be able to afford to produce such images in the first place.
Still missing it. You're talking about the supply side, I'm talking about the demand side. Two different things.
I guarantee that it's not worth a pro's time to go after 99% of the cases of copyright infringement. The last 1% is uploaders mentioned by louates, and the rare case of real companies doing it which you occasionally read about.