tedster - 4:12 am on Jun 4, 2011 (gmt 0) [edited by: Robert_Charlton at 4:28 am (utc) on Jun 4, 2011]
Here's a very informed criticism from ManuSporny, current chair of the working group at the W3C that created RDFa.
The False Choice
The schema.org site makes it appear as if you must pick sides and use Microdata if you want preferential treatment. This is a false choice! They even state that you cannot use RDFa and Microdata and Microformats on the same page as it will confuse their parsers – forcing Web designers to exclusively use Microdata or be lost in the morass of search listings. The Web community should decide which features should be supported – not Microsoft or Google or Yahoo.
...Microformats were created in an open and community-driven way. RDFa was created in an open and community-driven way. Schema.org was not, and if it catches on, expect to see it not scale over the long term and an increase in vocabulary lock-in to the major search companies. Which are you going to choose? Facebook's Like button markup, or Google/Microsoft/Yahoo's Microdata markup – you are being put into the position of choosing one of those exclusively.
[edit reason] fixed display of filtered name and link [/edit]
[edited by: Robert_Charlton at 4:28 am (utc) on Jun 4, 2011]