>Самая распространённая фамилия в Италии?
>Росси.

Действительно.

http://en.wikipedia.org/wiki/Rossi_(surname)
Rossi is an Italian surname, said to be the most common surname in Italy. Due to Italian emigration, it is also very common in other countries, including the United States, Brazil, Argentina, Uruguay, Chile and France. Rossi is the plural of Rosso (meaning red in Italian) although it is argued the surname derives from another source.
It is also a Finnish surname, not connected with the Italian one.
The name Rossi has been used frequently by various historical sources as The Rossi or Varangian Rossi in reference to an originally Scandinavian tribe that purportedly gave rise to the people known as the Rus' (people).

Якобы происходит от слова "красный", т.е. что-то вроде "Краснов". В то же время сами пишут, что прослеживается связь с Русами, считаемыми скандинавами.
Есть также финская фамилия такая же, якобы не связанная с итальянской.