Anything that can help stop this kind of madness is worth a good long look (yes, I don’t like the DiggBar any more than John Gruber, despite Digg’s assurances it’s safe), so I’ve had rev=“canonical” on my mind (yes, that’s rev, not rel). Chris Shiflett thinks it will save the internet, but Matt Cutts suggests what I’ve always thought: why not resolve short URLs to their long form and store/display them that way?
Who cares if there are n+1 different services providing short URLs point to the same resource? If we build our applications to resolve the short ones until they stop returning 301s or 302s (or a few other 300-series codes), then we’ll always have something that’s pretty close to the canonical URL. The short URL doesn’t need to be saved or indexed, it needs only be used in the transmission of the data (and then really only in the context of Twitter).
Digg’s attempts to put a frame over everybody else’s website, however, is evil. It it’s not only violates the user’s URL bar (and the publisher’s URL), it breaks any rational attempt to identify the canonical URL for the destination. They’ll tell you it’s okay, they use rel=“canonical”, but rel=“canonical” doesn’t work cross-domain, so that doesn’t mean much. And all this framing stuff makes me wonder why anybody would think Digg (or any other site whose business is based on monetizing the work of others) would respect a site’s rev=“canonical” preferences.