I knew intellectual property law was silly, but this ....?

Material Used On Set. If in the set dressing (including, without limitation, any props, no matter how inconsequential) or in any other manner, pre-existing material is used which may be protected by copyright, such as paintings, photographs, art objects, articles, book covers, magazines, newspapers, and even items of décor such as wallpaper (and the list could go on for pages) the written consent of the copyright proprietor of any such material must be secured. Note that the permission of the owner of the original or of a duplicate of the physical material is not sufficient. Thus a release to film in a particular location is not sufficient to cover the use of any artwork which may be present in that location – the permission of the copyright proprietor of that artwork is mandatory. Sometimes the “fair use” defense will apply, however Filmmaker should never rely on this limited defense without consulting an experienced attorney.

So in other words, if you're making a film, the company which manufactures any object that appears in your film can sue you if you don't get permission from them first. Kind of like reverse product placement.
Hmm, I wonder if I've just violated Atomfilms' IP rights by quoting this.