Re: Email?
The email system is itself decentralised in that there's a choice of MSPs.* It would be perfectly feasible for the MSP of your choice to also host your own self-generated public key. If you trust the DNS entry for Fred Bloggs's email server to be that for the Fred Bloggs you were looking for you can also trust it to be the entry for his key server. Fred himself can keep an eye on the key that's being served there to ensure that nobody nasty has changed it.
Why doesn't this happen? Because it's not required by the standard in use for email exchange. Optional add-ons are almost certainly never going to get traction.
* Even wider than the choice between Google and Microsoft!
Biting the hand that feeds IT
