I've been somewhat sceptical about the usefulness and security of URL shortening sites. Firstly, while I was still getting my head around Twitter, URL shortening just seemed like a pain in arse thing I had to do to fit something into that damn 140 character limit. How naive! Without the shortened URL presentation, most twitter posts and now, any other microblogging posts which is becoming massively popular, would be a mess. It would make the task of data sorting and searching exponentially more arduous.
The other thing which I LOVE is the tracking of click through's on shortened URL's, and for me, Bit.ly is the best I've seen. It really is interesting to test and see which topics, trends or formats get the most clicks.
The final main point was security. What happens if one of the thousand of URL shrinking companies goes out of business? I have heard this chewed over by Leo Laporte, Jason Calacanis, Gina Trippani and others many a time, and rightly so. I think the fact that Twitter has pretty much picked Bit.Ly as its golden child of URL shortening partners makes this not only the most enjoyable choice, but also the safest too, in my opinion.
Give it a try...