I just read an article that says the owners of ly Liyba is taking down sites it finds objectionable. Here is the link http://benmetcalfe.com/blog/2010/10/the-ly-domain-space-to-be-considered-unsafe/ www.tmgonlineservices.com
If it was possible, besides the myriad of other sites that do URL shortening as well. you can always just purchase a domain and shorten all your links yourself. You probably would have better tracking features and you wouldn't have to worry about "other" people changing around the rules on what is or is not acceptable
The best thing you can do is buy some type of short url script then get your own domain. I did this myself. I use my own short url from time to time....here is an example: Free Short URL Service I do not advertise the site often, but you are more then free to use it.
Read the TOS of the url cloaking service that you use. Sometimes the urls they provide expire due to inactivity or spam complaints. My webmaster has his own url cloaking website.
You always run the risk of this happening if you use 3rd party link shorteners. That's why I always buy a similar domain to my blog domain and use XSitePro to create redirect links for all my affiliate links.