Sometimes, it’s just annoying to look at this gigantic monstrosity of a URL. Just plain and very frightening. That’s why there are redirection services like TinyURL. What it does is that it redirects a small, tiny url to the giant one. Probably through a database query.
This allows people to not only shorten URLs, but also mask the originating URLs. Obviously this comes in handy as seen with Twitter where the messages are limited to 140 characters. Not unlike SMS services (character limitations), except that SMS doesn’t have need for such things like TinyURL.