In a recent message to the GData Python Client Library Contributors mailing list, Joe Gregorio outlines a new discovery capability for GData APIs. E.g. here's a document that describes the Buzz API. Look familiar ? To me it looks very much like a JSON version of WADL.
Joe goes on to describe the benefits of this approach and notes that it "allows very lightweight client libraries" and "the actual code for the client is very small". Maybe its time to revisit that Do We Need WADL post ? After all, the criticism levelled at WADL applies equally to this JSON variant.