Google today responded to widespread outrage at its recent crackdown on game videos on YouTube.

In recent days the company has sent out thousands of copyright infringement notices to video producers of game walk-throughs and Let's Plays. These notices deprive producers of advertising revenues. The notices are generated by an automatic system called Content ID.

"We recently enabled Content ID scanning on channels identified as affiliates of MCNs [Multi Channel Networks]," a YouTube spokesperson told Polygon. "This has resulted in new copyright claims for some users, based on policies set by the relevant content owners."

Let's Plays are videos showing game footage, overlaid with discussion from an independent host. They make use of extensive video game content, often copyrighted to games companies. Some of the content may also be copyrighted to separate companies, like music rights holders.

Content ID is YouTube's system for tracking use of copyrighted material. In the last few days, it has churned out an unusually large number of claims, aimed at video channels that generate advertising revenue, usually affiliated to a larger sales network like Machinima, often called Multi Channel Networks.

Some games companies, including Ubisoft, Capcom, Blizzard and Deep Silver, have stated that they have made no copyright claims, and have urged video producers to contest claims. They view Let's Plays as a useful promotional device.

"As ever, channel owners can easily dispute Content ID claims if they believe those claims are invalid," added the spokesperson.

Polygon will have more on this story in the days ahead.