There are a bunch of ideas mixed up in this that are somewhat alien to the web, which has only the URI as its native identifier.

On one level, all of the ID / profile tech out there is convoluted in the sense that it has a non-native semantic and/or interaction that is supposed to work in many web-native (or, otherwise, closed-system) contexts. This tech imposes its semantic and/or interaction on other contexts.

This can make sense sometimes, e.g., the ID / profile tech serves to unify different contexts (sites, social networks, etc.).

But, I think the ID / profile tech, being convoluted, offers almost no way in itself to understand the implications of unifying different contexts. So, closed system developers and individuals both have good reason to wonder if ID / profile tech is going to create more problems than it solves.

IMHO, I think we’d be better off focusing on a purely URI-based approach. And, as more convoluted solutions are out there, we should look to be sure that they degrade gracefully to the purely URI level.

For example, if, given a bunch of people, each has at least one URI that is unique to themself, other stuff (single sign-on, profiles, contacts / social networks) can be always optional on a per-user / per-context basis. And, it’s easier to implement each option in a variety of ways (e.g., a vCard profile is perfectly good for lots of stuff, but an hCard profile might work better for other things).