Jon Udell writes in his most recent column that some think that there is a "controversy" about the use of XML namespaces. This seems to stem from the sad fact that RSS never got a proper namespace assigned to it and is one of the hottest
schemas specs in the XML space right now. Sorry, there may people in disbelief, but the XML Namespaces spec is normative and referenced in the current XML 1.0 (Second Edition) spec. The empty namespace is a namespace.
Some notable experts — including Sean McGrath, CTO of Propylon in Dublin, Ireland — argue that namespaces should be avoided for that reason.
You can't avoid namespaces, they are automatic if you use XML today. If you don't declare one for your vocabulary/schema, you are contributing to a large cloud of "stuff" sitting in the "not part of any" namespace. The "empty" namespace (which essentially says "not part of any namespace") is the XML equivalent of a the "these are just some tags" garbage dump.