Eric Butler published an easy to use Firefox extension which captures session cookies from broadcast media such as public wifi networks. It allows anyone, to collect Facebook, Twitter, Flickr, etc session cookies and do anything with these accounts with just a click.
This is scarily easy!
I hope social network providers start implementing end-to-end encryption via https soon. Until then, be careful from where you access your social networks. On the other hand easy identity stealing brings social networking to a new level. 😉