Ask HN: The growing liability of URL shortening services

URL shorteners are used more and more (think Twitter's client e.g.) This means that vast amounts of hyperlinked semantic information rests on a few companies. The shortened URLs end up in may places in many forms. E.g. I use my twitter stream as a database of websites that I have found useful for work or otherwise. My database is useless if a shortening service goes down. For some companies, even downtime of a shortener costs money. Do you think that continuing the trend of relying on a few shorteners is increasing risk out of proportion? Many things can happen to a shortener: the company can fail, their security can be compromised by hackers, their CEO may choose to close shop and discover their spiritual self, and so on and so on. Thoughts?