He doesn't just own a lot of the media but also the biggest advertising company, Mediaset. In fact, there was also a similar lawsuit against youtube.

The prime minister and his lawyer posse has been quite active. They just sued a rival newspaper for asking questions that he deemed libelous: (in italian) http://www.repubblica.it/2009/08/sezioni/politica/berlusconi-divorzio-22/causa-domande/causa-domande.html