Forging URI schemes : best or bad practice?

I've posted already about International Virtual Observatory Alliance. It has a forum called IVOA semantics. Current thread is about relevancy of forging new URI schemes, fit for a large community of users (like astronomers) vs http URLs.

Guidelines for assigning identifiers to metadata terms

This document provides some simple guidelines for assigning identifiers to non-DCMI metadata terms (elements, element refinements, encoding schemes and vocabulary terms).

"Although these guidelines are mainly intended for metadata application profiles that conform with the Dublin Core Abstract Model, it is hoped that they are generic enough that they may be useful in the context of other metadata applications as well. "