This is common knowledge for most of you reading this, but I wanted a reference point for myself on the topic of shortened URLs and tweets. "Mentions" are a twitter feature where your twitter name (mine is @daveburkevt) is included in the tweet so that it comes to your attention. Unlike Direct Messages which can be sent only by people you follow, anyone can send you a Mention.
Now onto shortened URLs. Shortened URLs are web addresses manipulated in such a way so they use less characters, perfect for Twitter's 140 character tweet limitation. Typical URL shortening services are bit.ly, tr.im and tinyurl.com. Here's the deal. You don't know what is on the other side of a shortened URL. 99.99% of the time they're what you expect them to be, but there could be anything waiting for you, from an .EXE that loads a Trojan on your machine to placing you square-up against one of the Internet Warning Signs I blogged about in a recent Everyman. “Use extreme caution when opening images. Whatever you try, it is not possible to un-see something.”
Below is a sample mention including nothing but a shortened-url, my twitter name, and an avatar of some chick with cleavage. No matter how much cleavage in the avatar, do not click on that link. And while you're at it, block the user and report them to Twitter as a spammer.