On what do you base your guess? Because as I understand it, your guess is 100% wrong.
One, if I read the safe harbor stuff correctly, then if you ignore a DMCA notice it means you can now be sued for hosting the content. If a host decides they are willing to run that risk, I believe they can happily ignore a DMCA notice.
Two, basic business knowledge. YouTube partners with a lot of the major media companies, and taking down large volumes of their stuff in a way that looks dumb would harm their partnerships. Companies are very reluctant to bite the hand that feeds them.
Three, if someone could take down everything on YouTube by forging a zillion DMCA notices, I expect some enterprising troublemaker would have done it long ago just for the lulz.
Ok! Your turn. What's your evidence? Because that's what I asked for before and nobody replied.
Certainly I don't see anything in the law itself that prevents them from verifying that the notice actually comes from the entity claimed, or saying, "Hey buddy, are you sure you really own that?" Which is all I meant by basic checks.
Are you aware of some case law that demonstrates otherwise?