Let's forget the fact that this is being compared to SOPA and look at the concept as it is.
This is VERY problematic. The DMCA has been frequently abused against legitimate content and this would make a bad problem very, very, terrible.
I don't know if the copyright maximalists get it, but, like it or not, fair use and derivative works make up a MASSIVE part of our culture.
Not just nerds, not just crazed fans, but DECENT, NORMAL PEOPLE are making fair use works and derivative works.
You can't just extend a copyright law and dump the fair use concerns for later as if the concerns weren't important!
I know that fair use is just a defense for something but that doesn't mean there should be a legal battle almost EVERY TIME someone puts another's work in his own.
Automatic and permanent blocking of works due to suspicion of infringement is a terrible, careless idea and people should know why.