This issue was raised to some degree in another question, here.
URL shorteners pose several risks to users, which we as IT Security professionals should all be keenly aware of and sensitive to.
Primarily, the threat is that (absent special tools or plugins) you never really know what website is behind a shortened URL until you've clicked on it - at which point it is usually too late to avoid whatever threats lay behind it. This not only leaves the user vulnerable to intentionally posted malicious links, but also to the possibility that the URL shortner's service may be hacked and the links may be redirected en masse.
Secondarily, it has also been mentioned that some shortened URLs have a finite lifetime, leaving the links dead after awhile. This of course means that links which originally had great value on this site could eventually flat-out die irrecoverably.
I suggest we keep an eye out for these shortened URLs, both in actual posted URLs and in hyperlink destinations, and that users with edit privileges un-shorten them wherever they are found. Additionally, there should be a note added to the FAQ which states that shortened URLs should not be used here.