In much the same way that we don't frame links, or permanently remove flagged links, we would never return a short link that pointed to anything other than the link requested by the API, or by the user via an interface. It's a simple, deterministic API. The downsides of the proposed approach are far more extreme than any potential upside.
While I see what spohlenz is saying, I think what you've described here is the right way to do it. Once you start changing the target from what I submitted, I would personally be suspicious.
But, if the other shortener is returning a 301 'permanent redirect' isn't it fully within the letter and spirit of the http spec to forget it and remember the target.
If the shortener was only returning an 302 then removing from the chain would be suspect, but they are saying 'this link always points here, use it'
