Not sure if its what the poster above is talking about, but there's definitely a hash collision type attack that's common on Youtube with regards to classical music. The attacker in question uploads very standard renditions of thousands of pieces of classical music, and claims copyright on them. Content ID then flags any video using one of these pieces as potentially violating the rights of the rightholder.

The attacker then claims the video, and claims revenue on the video rather than taking it down. There's an appeal process which seems to work about 0% of the time, and after that the only recourse the uploader has is to submit a copyright counter notification, which becomes the start of a potential lawsuit.

The attackers in question will then typically relent if challenged with a copyright counter claim, but most videos don't get counter claimed once this happened.

This pattern of behavior seems so common that it has led to two interesting patterns of behavior that I've seen.

1) Any video that uses popular public domain music will be claimed not once, but dozens or hundreds of times, because there are so many channels operating this way now, and

2) If you post a video and immediately get hit with a huge wave of claims, rather than going through Youtube's process, most uploaders just delete the video, remove whatever audio caused the problem, and reupload.