Writing a bad review online has always run a small risk of opening yourself up to a defamation claim. But few would expect to be told that they had to delete their review or face a lawsuit over another part of the law: copyright infringement.
[…] censorship using the DMCA is common online. The act allows web hosts a certain amount of immunity from claims of copyright infringement through what is known as the “safe harbour” rules: in essence, a host isn’t responsible for hosting infringing material provided they didn’t know about it when it went up, and took it down as soon as they were told about it.
In practice, however, this means that web hosts (and the term is broadly interpreted, meaning sites like YouTube, Twitter and Google count) are forced to develop a hair-trigger over claims of copyright infringement, assuming guilt and asking the accused to prove their innocence.
As such, a very easy way to remove something from the internet is to accuse its creator of infringing copyright. Worse, the potential downside of such a false claim is minimal. […]
https://www.theguardian.com/technology/2016/may/23/copyright-law-internet-mumsnet