That's why what Joe Pistone did in the 80's was impressive. He was able to infiltrate the Bonanno family at a pretty high level.
He started with the Colombo family but some guys had doubts and he then switched successfully to the Bonanno Family, using his Colombo connexion as a back up for his story. That was smart.
When Lefty Ruggiero decided to put "Donnie Brasco" on record with the Bonanno he checked with Jilly Greca, The Colombo made guy who Pistone was around. Left did not check his past before that. It was his mistake.