Fun with Economics

This passage in New York Magazine's article on Bernie Madoff stopped me in my tracks:

People later wondered how Bernie could ruin so many people he seemingly cared about. But for decades he didn’t hurt anyone. In fact, there were many that he helped. “I lived off Bernie for years,” one investor says, and he was speaking for many. In all likelihood, Bernie didn’t pocket much of the money. He always paid out promptly, never shorted anyone. And money was flowing out all the time, in large quantities, one continual bank run. Hadassah, for instance, invested $90 million but over the years withdrew $130 million.

It sounds like he ran a collective money pool in which funds were shared and profits were delivered. I wonder how much longer it could have gone on, given that he had what every bank requires from its customers: trust. My question to you is: from a purely conceptual, theoretical standpoint, how was Bernie Madoff's operation any different than a bank?