I always wondered if all the made members of one organization ( for instance the Genovese family ) all know each other. I can imagine if you have around 250-300 made members in your organizations it would be hard to keep track of who's who.
There are also sometimes around 1500 associates of one crime family so it is impossible to know all of the associates. And I guess the mobsters also have relations outside their mob circle.

Just a somewhat funny story on this topic. Two mafia loan collectors in Philadelphia went to extort a bookmaker. The bookie said he was "with" Shotzy Sparacio who was a made member in the Philly mob. The collecters replied "who the F*** is Shotzy ?". The collectors had to later apologize to Sparacio.