ROME  Your college roommate is on Facebook. So are your cousins and colleagues and friends. But guess who else may find Facebook a great way to stay in touch?

Some people in Sicily who know a few things about networking.

In recent weeks, the Italian authorities have begun investigating Facebook discussion groups devoted to convicted Mafiosi, concerned that some members might be more than fans.

At the same time, a campaign calling on Facebook to remove pro-Mafia pages has been gaining momentum, while thousands of Facebook members have joined new anti-Mafia groups.

The debate spilled over from civil society to online society after recent news reports revealed that more than 2,000 people had joined Facebook interest groups hailing Salvatore Riina, the so-called boss of bosses, known as Totò, who was arrested in 1993 after more than two decades on the run; and his successor, Bernardo Provenzano, arrested in 2006 after four decades in hiding. Both are serving multiple life sentences.