As posted a couple of days ago it seems like the only penalty of perjury matter is that you are the copyright holder or can legally represent the copyright holder.
I also don't see what would stop someone from sending thousands of DMCA takedowns from TOR or some anonymising VPN, laying waste to an entire website for 10 days.
You're also required to have a good faith belief that the content is actually infringing. Not easy to prove you're not, but it's something.
The EFF's "dancing baby" lawsuit is still going; if they win that will set a stronger precedent for forcing copyright owners to first consider fair use.
These kind of cases make me wonder, what ever happened to the common sense.. The (classical) Roman law was probably the best system the 'makers of law' ever came up to. After that, it only went downhill.
perhaps dmca takedown notices should stipulate that the party should leave some identifying information, so they can be traced back. I suspect credit card info would be a good one.