@herrabre That's exactly the idea of the spec methinks ;) (and even possibly email server configuratiom discovery though that's best solved with SRV records.

Google were, as you probably know, on the webfinger train when it started out. But bailed on it, as with everything else open and good.

webfinger -> profile page -> rel=me works pretty good today à la !indieweb with !GNUsocial at least.