There's been a flurry of talk around URL shortening services like TinyURL and its many imitators of late. Some of the talk has been around which sites use which service, new ones launching, existing ones failing and everything in between. I, basically, don't care. The reason for this is because I don't get them (it's not the only thing, I don't get Twitter either).
The reason for this is because I have never found a situation where I would require a shorter URL. If I want to share a link with someone I copy the URL out of the address bar and paste it into the app I am sending, which typically will auto-link it. Job done. If it's on a post or comments and I want to keep it short, I use an HTML anchor tag, which is what it was designed for. At no time have I thought: "What I need is a shorter URL. I know, I'll go to a third-party site, paste in the URL I just copied, generate another link and then use that."
Another great reason for using the original URL is because it identifies the link, it tells you where it points, that was the whole point of domain names in the first place, so we didn't use IP addresses! Instead, someone invented shortened URLs which consist of the site's domain name and a random hash. It's completely unmemorable and tells you nothing about the link. When I click it I haven't got a clue if it's a useful site or a malicious one.
I have fairly long URLs, I've written about the benefits of having dates in them before, but I could just as easily have the post ID as the URL, one of my sites does use this method in fact. I could even drop the 'archives' bit of those URLs so all you get is http://domain.tld/postID - it's not much longer than a shortened URL. There are also plugins for some platforms to do this for you while allowing you to maintain the long ones for everything else. So most webmasters/blog owners could change their URLs to make them shorter, but there's no point!
One of the highest profile uses of URL shortening is Twitter. Shortening the URL obviously makes sense as you only get 140 characters, and the URL counts. From a UI perspective it's pointless, as I mentioned, shortened URLs don't mean anything, they're anonymous, so they might as well just link the work 'Link' as link text for the shortened URL. From Twitter's perspective, maybe they just store the shortened URL, thereby saving them a few bytes of storage, which, when multiplied by the number of tweets, equals a lot of storage. For a user, it doesn't make any different except that linking to an actual URL would be useful to check it before clicking it.
Ironically, there are now a ton of websites, scripts and plugins to expand shortened URLs. So now there are services to help me expand an URL that was shortened using another service when we could avoid the hassle and just use the original! Imagine the global time savings.