If you try to post, say, the latest Taylor Swift music video on YouTube without permission, don't expect it to stay up long. Swift's record company will notify YouTube's corporate owner, Google, of the copyright infringement, and Google will likely take down your video before Swift has found a new boyfriend.
But if you post a clip, say, of a Syrian rebel commander biting into the organs of his enemy, your content may well be safe. The graphic video that shows Khalid al-Hamad desecrating his victim's body has already been viewed more than 885,000 times, and duplicates of the clip can...