Chris at CSS Tricks has a great post in Little CSS Stuff Newcomers Get Confused About.
Bing Brings it On (RFDa, that is) at Semantic Web:
Bing webmaster help site that indicates Microsoft wants to play nice with whatever markup approach webmasters want to implement – microdata, microformats, or RDFa. The site mark-up overview on the page referenced says that Bing’s “crawlers do not prefer one specification over another. It’s entirely up to you to decide which of the supported specifications best fits your data.”
Contrast that with Google’s initial commentary about the schema.org structured data markup schema.