For years I worked in an organization that only developed internal training. The risk that my training materials would be seen by anyone outside the organization, let alone by anyone whose copyrighted material may have found its way into my training, was pretty close to zero. Of course this doesn’t make it right to use someone else's stuff in your course. I certainly wouldn’t want someone to take my material and use it how they wished.
I touched on this briefly in an entry I did on the topic of eLearning on a shoestring budget, but you really need to watch where all your photos, graphics, and even concepts and ideas come from. They are all potentially someone’s intellectual property.
I think this is especially important for the designers who are working as contractors or sub-contractors as I have done. I have charged customers thousands of dollars for the courseware I have developed. I’d hate to have to give it all back if my client was sued, and thereby I would be sued for steeling someone else’s material. Make sure you have the rights to use the material you put in your courses. In the long run, it may just save your bacon.