I just found out that if you use Google Chrome you can do a Google Image search by dropping an image in the search bar and Google will search for a "similar" image.
I tried this with one of my images and about 5 seconds later a link showed up where someone else had posted my image on their site. There were no credits listed or even any text around my image - just my image there among other images on someone's blog. Really strange, but now I am going to try lots of my shots to see if any others have been used without credit, or ... stolen ...
Thought you might all be interested.