One rule I have here is any comments containing a link that uses a URL shortening service gets removed, no questions asked. I do this because as Bruce Shcneier shows us those shortened URLs are a huge security risk. Cory Doctorow recently got screwed by a phishing attack via a good old URL shortened link:
I opened up my phone fired up my freshly reinstalled Twitter client and saw that I had a direct message from an old friend in Seattle, someone I know through fandom. The message read “Is this you????” and was followed by one of those ubiquitous shortened URLs that consist of a domain and a short code, like this: http://owl.ly/iuefuew.
Never click on a URL from a URL shortening service. You have no idea where they will lead you or what the page they link to will contain.