I think url-shortening is just a really bad idea in general. Certainly giving normal people the ability to track who clicks on their links is a good idea, but you don't need to obfuscate the url to do that. You could create a nice tracking service using urls like: http://digg.com/www.mysite.com/interesting-blog-post. The real cause of obfuscation is twitter's character limit, right? What does twitter gain by including anchor text in their 140 characters?

As usual a lot of people jumping in and engineering a solution without understanding the problem.

- Twitter links are almost never clicked on outside of the first several hours. 301 redirects will cause search engines to use the canonical URL as well. This Link Rot Apocalypse is largely a bunch of nonsense.

- People use short URL services to get analytics on the data they're sharing, not just to shorten the URL. People like their click stats.

I may be a bit dim here, but if you are doing the URL redirection your self, because you don't what someone else hijacking your content, and long URL's are not usable, then why not just create short URLs to begin with.

You wouldn't need any thing special, and people wouldn't need to shorten your url.

I'm all for creating a better solution for short urls, rev=canonical is not a good option.

The proposal mixes alternative urls with the idea of a canonical url. Besides being damn confusing (remembering the difference between rel and rev), it opens up security issues. Moreover, the 'rev' attribute is not included in HTML 5, making this proposal obsolete before it even starts.

I've written up a longer explanation of these problems on my blog for anyone interested:

http://cubiclemuses.com/cm/articles/2009/04/12/short-and-can...

Ultimately, if you want to discourage shortener services, you need to make short, meaningful URIs.