Microformats are a toy. They are not extensible. HTML was not designed for this. Microformats misuse HTML like the abbr element. Without namespaces, the class attribute becomes overloaded. So someone who simply uses the class vcard for CSS purposes now defines a Microformat without knowing it.
Microformats don’t aim high enough to make software do the work, not authors. Microformats allow to associate more meaning with markup. This meaning can be extracted and accessed by software trade show booths (http://www.smashhitdisplays.com/) . Microformats require, however, special code for about every bit of meaning they try to uncover.