We Are the World

I think the unifying theme is money:

In the 1920s, Lucky Luciano was closely allied with the top Jewish gangsters Meyer Lansky and Bugsy Siegel. In the 1960s and ’70s, Luchese mobsters were partners of a sort in heroin trafficking with the Harlem drug kingpin Leroy (Nicky) Barnes. In the 1970s and ’80s, the Gambinos had working relationship with the Westies, an Irish-American gang based on the West Side of Manhattan.

For many years now, Albanian gangsters have been closely aligned with Bronx-based members of the Gambino family. In the 1970s and ’80s, Spiros Velentzas, the so-called Greek godfather of organized crime, was closely affiliated with the Luchese family.

That's Jerry Capeci, proprietor of the mob's leading "social networking site" (tee hee!), answering questions about the mob at a New York Times blog. Apparently you don't have to be Sicilian. Apparently it doesn't even help.