There have been reports over the last few days of an AT&T security breach. A group of hackers was able to obtain the e-mail addresses of over 100,000 iPad users from an AT&T server. The hackers notified Ryan Tate of Gawker, who wrote about the incident a few days ago.
If you want a comprehensive overview of the incident and the latest developments, Nick Bilton of the New York Times wrote a good article on it last night, including reports on an FBI investigation, correspondence that AT&T sent last night to its customers, and comments from the hackers seeking to justify their actions.