That said, I agree with jandrese's point about key management -- low-security key management solutions shouldn't prevent people from taking a high-security approach. Seems like the ideal situation would be if the really paranoid people end up naturally testing the low-security infrastructure as a side effect of doing their paranoia stuff. E.g. if the gpg client was set up to automatically report discrepancies between a user's personal web of trust and a presumed-authoritative keyserver.

That said, it's unclear to me why Signal wouldn't have worked for Snowden -- interested to explore details here.