Are users of social networking sites subject to data protection law, as controllers?

Social Networking Sites (SNSs), �blogs�, �twittering�, etc., are rapidly expanding phenomena. Millions of people from all over the world, mostly but not only young, are sending ever-increasing amounts of information to websites, to be shared with others. The information ranges from photographs of themselves, to videos of themselves or others, to comments on and pictures of public events - such as the recent demonstrations in Iran after the contested elections there.