When I provide links from this blog, I don't shorten them. When I get a link in an email, I always hover over it to see where it leads, in case it's a phishing email. But when someone emails you a shortened link, or tweets a shortened link, how do you know where it leads? It might be a phishing link. Or it might just be that cat video you've seen too many times already.
Years ago, Joshua Long wrote up a summary of how to see where a shortened link goes
before you click it, and he's been updating it pretty regularly. He covers TinyURL, bit.ly and its relatives like on.fb.me, goo.gl, is.gd, and many I've never heard of. There's even a site you can paste a shortened link and get back what it redirects to. Not all links will be worth this treatment, but many will. It's nice to have a summary of how to check them before you follow them.