//Even the biggest players can suffer from hacking. In the news today is a story about the details of 250 thousand Twitter users being stolen during a sophisticated attack.
Twitter have warned affected users to change their passwords.
More details: http://blog.twitter.com/2013/02/keeping-our-users-secure.html
//A criminal gang targeted Facebook users and stole their passwords, bank card and account numbers, and other personal information.
They used phishing techniques to install malicious software on their victims computers:
http://www.bbc.co.uk/news/technology-20693213
Moral: be very careful where you enter your user and password!