Not too long ago, famed TV talk show host, Oprah Winfrey found herself in a lawsuit with two professional photographers. At odds were some images found in a book she wrote called "Make the Connection." Both the photographers and Winfrey were in dispute about who had rights to the photos and how they could be used.
The suit took was settled after three years in court. Winfrey was trying to protect how images of herself were used and the photographers were trying to protect any relevant copyright violations of their work.
It's not likely that the casual user or seller of stock photos would end up in a serious situation like this one, but it does illustrate how important photo licensing agreements are. It's also a warning to anyone who attempts to use an image that is owned by someone else. Any time you use a photo, make sure you know its source and if there are any legalities that affect the use of that shot.