A couple of comments on bioGUID have appeared. Egon Willighagen posted a short note on Nature's Semantic Web for the Life Sciences forum, to which I've responded by clarifying what bioGUID does.
Leigh Dodds has a note on the All My Eye blog. Embarrasingly the example Leigh used was broken for a while because the California Academy of Sciences DiGIR provider was offline, but it's back now. This is one of the perils of federation. When it's online (or the metadata for the record is already in the cache), it looks like this (if your browser supports SVG):