Facebook e-mail notifications breach privacy

Shortly after joining the social networking site Facebook, I received an e-mail telling me a friend had "written on my wall". Within two clicks I was logged-in and had full access to her account.

At first I was very confused -- I had only used the site for a day or two and thought I may have done something wrong but when I managed to change her status message to "is being hacked", I knew something was wrong.

I logged out (of her account) and then tried clicking on the link again to try and recreate the effect but it didn't work. However, when I opened the main Facebook page and typed the first letter of my friend's name, the browser had somehow remembered her username and password and allowed me to log into her account at will.