Here's another place you might not want to find your grandparents' names: the diaries of FBI special agent Max H. Roder, now for sale on eBay.
The diaries from 1931 to 1937 are his narcotics work in Philadelphia Pa. Diaries from 1938 to 1959 are New York City work except for a brief period Sept 46 to Sept 47 when he went back to Philadelphia Pa. It appears the New York City cases were mainly targeted again Italian Americans in Little Italy. You'll be amazed how many people smoked opium in NYC. [Link, via Boing Boing]