Personally, I'm starting to be fed up with them. They can be used to disguise links to spam and self-promotion. Security experts are recommending against them, such as in this blog at ZDnet:
The safe thing to do with normal links is to hover over them to see the actual domain that you will be sent to. With URL shortening, that doesn't work. I have figured out how to preview tinyurl links using preview.tinyurl and yes I now have a cookie to always preview at tinyurl. But, there are many more sites for shortening that I've never heard of and have no idea if they are trustworthy. I just saw a new one today in this post. I checked out the site the long way around -- the safe way -- and found that the way that they do previews is different than tinyurl. I really don't want to have a cookie for every one of these sites. I still have no idea if isgd can be trusted anyway.
Finally, these sites can be hijacked to send every link to spam or malware as recently happened with cligs: