It's easy for websites to make a profit selling online advertising. All they have to do is avoid paying for content.

Sites brimming with pirated movies and television shows are being supported, inadvertently, by major marketers that buy ad space on them. Thanks to the rise of automated ad-buying technologies, more ad dollars are flowing to sites with stolen copyrighted content than ever before, ad executives say. Who should do the policing is a matter of debate in the industry.

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