The only requirement is that the DMCA claiment swear, under penalty of perjury, that they are authorized to make the demand (they are the copyright holder or authorized agent). No other penalty / liability against the notice server is provided for in the statute.
Unless I'm misremembering, that was not a part of the original statute & was added later. The criticism I gave was fairly common immediately following passage of the DMCA.
(f) Misrepresentations.— Any person who knowingly materially misrepresents under this section—
IANAL, but those two words "knowingly" and "materially" are extremely huge caveats that should make it very easy to avoid any liability for carefully crafted false takedown notices.
The only requirement is that the DMCA claiment swear, under penalty of perjury, that they are authorized to make the demand (they are the copyright holder or authorized agent). No other penalty / liability against the notice server is provided for in the statute.
Relevant portion: 17 USC 512(c)(3)(A)(vi) http://www.law.cornell.edu/uscode/text/17/512