I believe Youtube has a similar system called Content ID. It is meant to automatically file copyright notices, so the revenue on the videos goes to the copyright holder. There are a lot of very easy ways to avoid it, which is why copyrighted material is all over youtube. You can speed up the video by a few %, change the saturation of 1/4 the screen, put a border around it, and then the only way it can be found and DMCA'd is if the copyright holder does it personally.

And also, there will always be websites that blatantly ignore DMCA notices just like how pirate bay does. If this system does actually come into play, many people who don't want to pay for porn would be pushed into piracy, making a huge market for a website like that.