Google does a good job of filtering pornography uploads to YouTube but refuses to apply the much easier technical challenge of filtering unlicensed music or movie uploads to YouTube.
Wait, what? That is exactly what the ContentID system does.
And how is that a much easier technical challenge? Google can rely on users to report porn, because the average Joe knows it when he sees it. That's basically free. To filter unlicensed works, Google must scan and fingerprint every licensed music and movie in the universe and compare them to the the fingerprint of each uploaded video. And from what they claim, 5 hours of video are uploaded to the site every second.