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   The term is used in metropolitan areas associated with large Italian-American populations, such as New York, Ohio, Connecticut, Pennsylvania, Massachusetts, Rhode Island, and New Jersey.[6] In other areas, terms such as "Mario" (Chicago) and "Gino" (East Haven, Connecticut, Toronto, Montreal) have a meaning similar to guido.[4] Although some Italians self-identify as "guidos", the term is often considered derogatory or an ethnic slur.[4][7]The term caused controversy in 2009 when MTV used the term in promotions for the reality television show Jersey Shore.[4] This spurred objections from Italian-American organizations such as Unico National, NIAF, the Order Sons of Italy in America,[8][9] and the internet watchdog organization ItalianAware.[10][11] Although MTV removed the term from some promotions, it remains closely associated with the show, and some of the cast members use it regularly to describe themselves while the females sometimes refer to themselves as a "guidette."

more info here> http://en.wikipedia.org/wiki/Guido_%28slang%29