In a recent question a link to a site was included that had been shortened using tiny.cc.
The link was inoffensive, however you could not know that for certain without clicking through.
So I'm wondering if we should adopt the policy of discouraging such indirect links. After all, there is no need for url shortening services here as even the longest possible url can be presented as this.
If we allow these URLs, it is only a matter of time until someone abuses them to post inappropriate content.
I completely agree, we shouldn't be linking to redirection services. Furthermore there is no need to, since there is no tangible restriction on post length. The reason given by the user in the question you refer to was bogus anyway.
System policy falls just short of forbidding them outright. They should be discouraged for the sake of clarity and users should feel free to un-shorten a link that has no reason to be shortened.
Keep in mind, there are a limited instances where shorted links are necessary. For example, try linking to anything in the Internet Archive's wayback machine or a screenshot on browsershots.org. The markdown chokes and it just won't work without an intermediary. This makes an outright ban problematic.
How about encouraging people (if they are going to use short links) to use Google's one since it checks for malware etc.
Otherwise, maybe the SE guys can work on their own shortener since that means that they know it will last as long as they do and also you could do what Twitter do (or used to, I don't know anymore) and use Google's Safe Browsing API to check the links.
Even in the case the service that provides the short URLs check the URL for malware, using full URLs in links help who reads the post, who can decide if it's worth looking at the linked page. Supposing the link is reported in an answer, who reads the answer can see if he has already visited the page without actually visiting the page; this would not be possible if the link contains a short URL.
