(I'm sure several Sopranos actors are on this list)
A lot of the today's notion of snitching has its origins in the mob world, since they were the first to popularize the so-called honor code and then publicly Start Snitching on each other to save their own asses.
A few weeks ago the Times dropped a little article about how the entire mafia is basically a wrap due to snitches.
Italians Start Snitching (NY Times)
To all the Italian-Americans out there who are dropping dimes on each other and keeping stereotypes alive, you are the Snitch of the Week.