Some great data from my one-time colleague Peter Mika. Based on data culled from 12 billion web pages, RDFa is on 3.5 percent of them, even after discounting “trivial” uses of it. Just look at how much that dark blue bar shot up since the last measurement, some 18 months earlier.
Also of note: eRDF has dropped off the map. hAtom and hReview are continuing their climb.
-m