> The longevity of short URLs (or any form of redirect) is their primary drawback. Having one company bail out another is not a long-term strategy. The only long-term way to make sure redirects continue to function is to have some kind of open, federated redirect service (which might be what 301works is trying to achieve). However, the kind of flexibility inherent in a federated service implies that the links would not be very short (e.g. 301works.com/bit.ly/abcdef), so they would at best be a backup solution.

Or someone specifically concerned about longevity: http://purl.org (those aren't short either though).