Mozilla didn't seem to learn from the first shot at trying to control the FeedIcon. Now they released usage guidelines. The usage guidelines are not legally binding, but I really wish they would have avoided this. For instance, in the visual guidelines they recommend...
The feed icon (or confusingly-similar variants of it) should not be used in the following contexts: as, or incorporated as part of, an application icon, a web site logo (including a favicon)
the icon should not be displayed in a color other than orange (or black where the use of orange is not possible)
This, of course, means the FeedValidator is not in compliance. I assume Sam won't embarass Mozilla for this stupidity, but I wish he would, if only to tell Frank Hecker that we won't be following his guidelines.