Not really, but in Palermo and the surrounding area it sometimes seems like it.

In the east of the island (Catania excepted) there is very little mafia activity at all. In fact in the extreme north east and extreme south east (where my relatives comes from) you'd be hard pushed to find much activity mafia at all. When something very occasionally does happen its usually overspill from Catania, and when it does the papers go nuts about it.

Organised crime in the south east is usually not related to cosa nostra, its more people trafficking or non cosa nostra drug smuggling and various other coastal / smuggling crimes. Large stretches of remote coastline encourages that..