The biggest Ponzi schemer—that we know of—Bernard Madoff is serving a 150-year sentence in federal prison, a far cry from his life between homes all over the world. But apparently he likes being behind bars! His daughter-in-law Stephanie Madoff Mack reveals what he said in a letter to her, "As you can imagine, I am quite the celebrity, and am treated like a Mafia don."

Mack, who was married to Madoff's son Mark, who killed himself last year, says she sent Madoff a letter telling him about the moments in his grandchildren's live he missed, hoping to make him feel bad. But Madoff wrote about his happy times, "They call me either Uncle Bernie or Mr. Madoff. I can't walk anywhere without someone shouting their greetings and encouragement, to keep my spirit up. It's really quite sweet, how concerned everyone is about my well being, including the staff ... It's much safer here than walking the streets of New York."

Mack, whose interview with 20/20 will air tonight on ABC (she says she'd spit in Madoff's face if she saw him today), also said her husband was driven to death by his father's deception, "My husband was in terrible, terrible pain. He was so deeply hurt by it all, that he just, he, he just couldn't move past it."