Earlier quoted context omitted.
> decentralized reputation through cert validation? Certs are pretty dang centralized. Also, Your second sentence needs a bit more fleshing out because it doesn't follow.
Certs are certainly decentralized. You can create your own root, share them, etc. There a several highly trusted roots that are chosen by OS makers, not centralized. Some roots are quite big but what part is centralized? Chain of trust is a decentralized reputation protocol and we use it frequently and effectively.
A contributing factor is that the culture that grew around them makes it uncommon to be able to manipulate your own certificates. If you set up a Web page with your own root cert, you can be sure it will never grow.