I've found this an interesting discussion. To my mind, the other side of the question is: what are the odds that you'll find out that someone stole your work? OK, if a company were to misappropriate a photograph and use it in a Super Bowl commercial, you might see it and know to complain. But if that same company took an image and used it in their annual report, what are the odds you'd ever see that? If one were so inclined as to misappropriate images, I bet he/she would get away with it 99% of the time simply on the basis that the odds of the actual photographer seeing the image would be miniscule.