I only just read Jim Hendler's piece from last month "shirkying my responsibility", in which he states that the W3C Semantic Web vision was never about a global shared ontology at all:

"Get it - we are opposing the idea of everyone sharing common concepts."

This seems odd to me, because if that is the case and all communication on the semantic web is local then why is the basic system of identity the URI, a global identifier scheme?

On the contrary, I suspect that the W3C Semantic Web is predicated on global agreement: that all RDF documents containing a URI should use it to identify the same concept, otherwise the whole RDF inference stack breaks. A global ontology that's defined in lots of inter-connected pieces scattered around the web is still a global ontology.