What Pete described is exactly what happened to me. My parents immigrated from a very rural area in the Napoli (Naples) region and I spent my summers as a boy there. Because my parents were basically uneducated I learned the dialect of the region. I can understand 'real' Italian but I only really speak my dialect. I went back in 2007 for the first time in about 15 years and definitely noticed that there was less dialect around. When I asked my family about it they said that basically because of how open communication has become due to telecommunications and travel technologies that they now use 'real' Italian as the local dialect has a stigma associated with it of being uneducated.
But to go back and answer the question.....like Lcadio said its fee-h-kee