It seems a little shaky to me, because: 1) bit.ly could reject the link at submission time, instead of at the time of usage. This would eliminate the whole pro

It seems a little shaky to me, because: 1) bit.ly could reject the link at submission time, instead of at the time of usage. This would eliminate the whole problem. 2) bit.ly could follow the link, unshorten it, and then shorten the original link. This would eliminate these concerns.