Apparently it is possible to navigate to any post anywhere in videosift from any of the channel sub-domains, yielding some rather undesirable valid URLs, e.g., http://kids.videosift.com/video/Porn and http://lies.videosift.com/video/Shoah-by-Claude-Lanzmann-Landmark-Holocaust-Documentary. I'm not sure how to prevent that from happening, but it's probably best if URLs like that don't turn up anywhere.