Point, but I'll refer you to my following sentence: 'The fact that I trust you to vouch for employees of Acme Widgets means nothing about whether I trust you to vouch for members of a political party.'

The Web of Trust assumes that I trust anyone to vouch for everyone (interesting, TLS — itself also a product of 1990s crypto-thinking — makes the same assumption). But I simply don't. I don't trust my nearest & dearest family & friends to vouch for every identity I care about. But I do trust some of them for some identities.

I trust myself to validate possession of any key. I trust my employer to validate possession of keys related to its work, but not keys related to, e.g., my family or my blog. I may trust one of my brothers to validate keys related to his immediate family, and maybe I trust two of my brothers to jointly validate keys related to our family, but I don't trust them for work, or my blog. I may trust my blogging co-admins to validate keys for roles in the blog, but that doesn't mean they get to validate keys for identities at my employer, or validate keys on behalf of my parents or children.

I could use different email addresses for each identity (I-the-employee, I-the-son, I-the-blogger), and have each identity trust only those who are pertinent to it, but that makes PGP more, not less, difficult. And it's certainly not the model that PGP advocates.