I love using bit.ly, tinyurl.com and is.gd.
I use these URL shortening services for a variety of reasons, but mostly because they allow me to send URLs to people who know little or nothing about the web – specifically people like my mom. Although her and her peers are capable of using email, IM, and other web services, they are incapable of detecting when a URL has been artificially wrapped:

A screen-cap of an email about mustard!
A user, not knowing any better, would click on the highlighted URL above and load a page other than the one the author originally intended. This leads to an embarrassing breakdown in the conveyance of information, which would be horrible in a business or professional situation.
An argument can be made that these URL shortening services should not be used as they introduce and unnecessary dependence on a third party service. I contended this point with three others:
- As cited above, the use of long URLs puts your audience at risk.
- Assume that the lifetime of the shortened URL is low, and that it will only remain relevant until the recipient clicks through to the final non-obfuscated URL.
- Once the recipients browser has loaded the final URL any bookmarks they make would reference the final, un-shorted, URL.
One Comment
you sure as heck are relying on these services to do the right thing. Do they have any SLA ?