data portability for URL shorteners

Yesterday, Dave Winer wrote:

One easy way to lower the cost of URL-shortening is to use our own domain names in place of tinyurl.xom, bit.ly, tr.im, et al. Any one of those services could take the lead here by allowing for that. Let me map my own domain onto theirs, easily back up all my data, and give me the ability to switch services when I want, or when I need to.

I would call it "data protability for URL shorteners". It's what I've been trying to push for more than a year by urlborg.xml (and was actually inspired by an older post of Dave Winer) .