This happened some time ago, but we forgot to mention it. Flickr expresses information about images and the licenses associated with those images using RDFa. In fact, Flickr was one of the first services to adopt RDFa and use it to express metadata about the contents of the web page.

[...] This post was mentioned on Twitter by misscj and Andy Murdoch, bdarcus. bdarcus said: Guess I missed it too; that Flickr is using RDFa – http://rdfa.info/2011/01/25/flickr-uses-rdfa/ [...]
26 Jan 2011 at 23:34