No, it's not according to the watchdog, it's exactly what's happening: the "like" button is a clever bit of social engineering to facilitate user tracking across websites.
Website owners should think twice about using these kind of things. Not only out of respect for users' privacy. These trackers aggregate data across websites which website owners don't have access to and are the basis for Facebook and co for selling adverts to the sites. With the data gathered they can, and do, happily talk to the competition about the kind of visitors that visit a site. By placing the button on the page you give these companies to hoover up data about your customers but they don't have to share this data with you.