Fugitive Mob Boss James "Whitey" Bulger Lived Like a Beachside Retiree

Garrett suggests, "(Bulger) probably had an informal pipeline, money, cash that he had access to," perhaps a few friends "who fed him money during direct handoffs." In this scenario, it is likely that the contact would meet him in a public spot and "hand him a brown bag with money in it," Garrett said.

This, he said, is how the Whiteys of the world operate. And, as such, unless authorities know who was aiding him, "You have no trail. No electronic trail, no digital trail."

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Younger criminals would probably have a harder shot at success, he said. Bulger likely never grew accustomed to the digital world most people today live in. He may never have used e-mail.

Authorities say bin Laden too stayed off the grid in his hideout in Pakistan, helping him avoid capture.

It is also likely that Bulger avoided his old life as an alleged mob kingpin. "What happens is, people go back and they touch their past lives and when you touch your past life, you're going to get caught," said Garrett.

"He's been lucky and he's always been disciplined."

ABC News' David Wright and Richard Esposito contributed to this report.