A business idea: Service to query the long urls for bit.ly and other shortener links which will also provide caching and history (if redirection changed, we would get to see when and from where)
The history option sounds very interesting. For example, the owners of "ethical" URL shortener is.gd do just change shorturls if they like a particual shorturl (e.g is.gd/td leads to tweetdownload.net, a site owned by the same company as is.gd. I know for a fact it previously led to a different URL.)