You know about Rickrolling, right? (e.g. Here, this is my theory on quantum physics)
On the Twitter I use a URL-shortening service called Bit.ly. It takes long URLs and scrunches them. There are other websites like Tinyurl and the even slightly shorter Ow.ly, but I like using Bit.ly for some reason.
Bit.ly (and the other URL-shortening websites, I presume) use some sort of algorithm to reduce URLs to their small form. It really has nothing to do with *who* is requesting the shortened URL -- the smaller URL will be the same.
One thing neat about Bit.ly is it will show you how many clicks have gone through one of their shortened URLs.
Out of curiousity, I picked the most-viewed video of Rick Astley's "Never Gonna Give You Up" (over 18M views thus far) and Bit.ly'ed it.
I personally want to thank Bit.ly and the other URL-shortening services for making Rickrolling possible.