There are a number of sites that will mask or shorten a URL (TinyURL, TubeURL, URLZoom, W3T to name a few). For example, you can take a long URL (http://www.bukisa.com/people/skimblecat) and make it shorter and more user friendly (http://tinyurl.com/cs8kos)
The biggest benefit of this sort of service is convenience - it's way easier to type the shorter URL. This is especially useful when using something like Twitter that restricts the number of characters you can use in each message. You can also use this service to cloak affiliate links.
Of course, there are potential downsides. You don't know the real URL you are being sent to (note: tinyurl has http://tinyurl.com/preview.php that lets you preview the site for 10 seconds before you go, so you can stop your browser if needed). The Bad Guys are capitalizing on this type of service, to redirect people to malware infected sites.
As always, never click on a link from someone you don't know. And be cautious even if you know the person. Really, just be paranoid like me :-)