> I have seen the subject come up regarding organizations that carelessly bulk-send DMCA notices based on quick searches for possibly infringing material with little, or sometimes any, effort to confirm. Though I suppose that wouldn’t be “good faith”. But wouldn’t that be a negligence standard?

Both in terms of real problem and constitutionality I think a negligence standard is more defensible than strict liability.

> If the DMCA regime shifts all the costs for a false statement (even if not a “knowingly” false statement) to the recipient (and/or their hosting provider), that’s a problem.

To be fair, the DMCA doesn’t shift any costs in that direction; in the absence of the DMCA safe harbor provision that the notice/counternotice process is part of, the notice recipient would be exposed to all the same costs as they can be under that regime, and the host would be exposed to additional costs. The safe harbor regime only gives the host an option which, if followed, removes any liability they would otherwise have, first (on the notice side) to the purported copyright owner, and second (on the counternotice side) to the target of the notice.

Which is why counternotice compliance is spottier than notice compliance: hosts are confident that, even before the safe harbor, they have no liability for an unnecessary takedown, so they don’t care about the part of the safe harbor tied to counternotice compliance.