Short URLs are useful both for space-constrained (e.g. microblogging, mobile) and manual entry (e.g. printed, spoken) applications, however URL shortening services are causing problems of their own (e.g. linkrot, analytics, security, etc.).

The rel="shortlink" proposal (which is made available with copyright, patent and trademark waivers) solves this problem cleanly, with little or no risk of collateral damage.

The proposed alternative (rev="canonical") also has numerous problems (e.g. HTML 5 deprecation of "rev", taking rather than giving canonical-ness, dangerous failure modes resulting in SEO problems, etc.). Furthermore the rel="shorturl" alternative is both confusing with many permutations (short_url, shorturl, shorturi, etc.) and affected by intellectual property issues (copyright protected specification, trademark status claimed by shorturl.com, unknown patent status).