There are websites which can only be reached by using the "www" in the url. When having an ordinary website hosting package, it's normal to have that redirection to the www-adress, but there are some major brands, where the redirection doesn't work.
For example: Swisscom Mobile. The biggest mobile phone service provider in Switzerland still doesn't redirect users from http://swisscom-mobile.com to http://www.swisscom-mobile.com (interestingly for http://swisscom-mobile.ch it works). I already informed them about that failure some months ago, but they haven't reacted.
That's a small usability-failure, but nevertheless it's bothersome if you are used to write urls withouth the "www" in front.
Another website that doesn't work without the www in front is the website of the University of Zurich. Well, http://uzh.ch/ works, but if you have a subdomain included it doesn't work. (e.g. http://ifi.uzh.ch). I heard that's because http://ifi.uzh.ch is used for the intranet)
Question: Do you know any important websites that don't work without www in front?