It’s no surprise that YouTube users have illegally uploaded hundreds of full-length films to the site. What does seem odd, however, is that in several cases, movie studios have apparently not tried to stop them.

The Wall Street Journal reported Friday morning that hundreds of films, including “blockbusters from Walt Disney Co. and Sony Corp.’s Columbia and Tristar studios,” are available on the world’s largest video-sharing Web site. This is nothing new — YouTube has battled allegations of copyright infringement since at least 2006, when MTV owner Viacom sued the site — but it has plummeted since YouTube debuted an automated system for handling illegal uploads in 2007.

That system, called Content ID, works against a giant database of 15 million movie and song samples. Studios and labels submit clips of their content to the database — some as often as every day — and choose what they’d like to do if a match is found.

They can have the offending video deleted, which results in that copyright-violation sad-face screen we’ve all seen. They can place an ad next to the video to mon­etize it. They can also choose to do nothing, a path few producers take.

“YouTube’s Content ID system gives rights holders an automated way to identify, block, promote and even make money from their content on the platform,” a YouTube spokesperson said in a statement. “We partner with more than 4,000 media companies on Content ID.”

Disney and Sony did not immediately return requests for comment on how they use Content ID. Yet as of Thursday morning, you could still watch “Peter Pan,” “Snow White and the Seven Dwarfs” and “Fantasia” on YouTube ad-free. While that could mean the uploaders tricked the database by garbling some part of the film, it’s more likely that the company did not submit clips from the films to the Content ID database, omitting them by accident.

That seems an odd oversight for an industry that has policed piracy and copyrights so zealously in the past. Disney, in particular, is known for its role in the late-’90s extension of the Copyright Act, which kept Mickey Mouse out of the public domain for another 20 years. And the Motion Picture Association of America, to which both Disney and Sony belong, played a major role in pushing the controversial Stop Online Piracy Act to the House floor in 2011.

Disney pulled several films from YouTube on Thursday, apparently in response to the Journal’s inquiry. Uploaders are one step ahead of the studios, though. “The Lion King,” “Rango” and “Back to the Future” are still online — albeit on Vimeo, a smaller site without the hassle of Content ID.

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