namespaces considered harmful
(This article is a stub, feel free to expand upon it)
The mixed namespace approach has already been tried by *numerous* others since 1998 and has failed on the Web.
OTOH, XHTML + semantic class names has seen widespread adoption among the web authoring/design/IA/publishing community. Microformats is leveraging the approach that is both working better and frankly dominating in practice on the Web.
Namespaces are actually a *huge* negative. Search for: