I tried to onebox a youtubevideo and a soundcloudpodcast in the category description. It did not onebox. It got ignored.
The purpose is to let the user get a good overview of the category quickly by showing an introductory video and soundfile. A title, a few words, a video and a soundversion. Should also work for group and tag descriptions.
Can it? Should it? Is it intentional? Is there a setting?