So Proof of Personhood uses a Key Signing Party to demonstrate you are a human? Could a group of bots simulate this if no human is present?
Also they are attempting to protect against Sybil attacks, with Proof-of-Unique-Human. This is a much harder problem, especially without any PII.
PGP used to have these parties and they were only attended by very security aware people, because the majority of people would not bother and rather trust a central authority.
I hope that something like this works.