A DMCA notice is
not a legal action though. It's not filed with a court. It's basically a C&D letter send to a host or ISP that is serious business for the host or ISP (b/c they could lose their Safe Harbor protections if they don't follow it) but the only penalty that the letter-sender might possibly incur is a charge of perjury. The take-down notice basically states "I believe that X is really my copyright and that I have not authorized it to be distributed in such a manner. I agree that I believe this is the truth under penalty of perjury."
The statement is nebulous. To prove perjury, you would have to prove that they did not believe that the copyright was owned by them. Proving that is a tall order in court, and perjury seems like a slap on the wrist compared to the damage that can be down when the power of the DMCA-take-down-notice is abused.
This is why DMCA notices are basically an unchecked power given to 'rights holders' in a world ever everything that is produced gains an implicit copyright.