About 98% of Trackbacks are spam. Obviously that can’t be addressed with a new spec without breaking backward compatibility. (For added humor, see the front page of the Trackback Development Blog.) The charter of the new trackback abandons the only thing that made Trackback interesting, and incidentally one of the things it was created for, content aggregation and category aggregation and other applications that don’t require a link at all. (Essentially a push application of what everyone uses tags for now, it was way ahead of its time.) In the meantime, they’re re-inventing Pingback with XML-RPC replaced by Atom/REST.
There is talk of pushing for Trackback to become a standard. A few of the problems with Trackback are immediately apparent: horrible internationization support, bad auto-discovery, proclivity for spamming, no verification, historical baggae of category junk, bad spec. Fix all these and you get… pingback. Pingback is big enough now to make a blip in Google’s markup survey, and is supported by a wide range of platforms. The question is whether people are going to want to support an existing and robust standard or want to put their name on something new, the global “not invented here” syndrome where everyone wants their 15 standards of fame. (As someone who has been involved in several standards myself, I admit the draw is strong.) What Pingback does need is a better advocacy site, like atom has.