Ten years ago, when electronic stock trading systems were emerging as the future of the financial services industry, Wall Street turned to a familiar face for help in adapting to the new technology.

Meanwhile, numerous charities, well-heeled New Yorkers and Floridians, as well as a smattering of celebrities, were turning to the same face to serve as caretaker for their philanthropic endeavors, family investments and personal nest eggs.

It was the handsome, calm, self-possessed face of Bernard Madoff, now charged with masterminding perhaps the single largest securities fraud in history.

As allegations emerge of a decades-long scam in which investors were paid off using cash from new investors rather than actual gains -- a classic Ponzi scheme -- regulators are facing tough questions over how numerous red flags were missed.

Wall Street veterans believe the answer lies at the heart of the capitalist system -- a system that relies on trust.

“He couldn’t have done this in Venezuela or Iran. You’ve got to do this in a democracy that operates on trust,” said Bruce S. Foerster, president of advisory firm South Beach Capital Markets.

Madoff, 70, was a well-known and widely trusted figure. His expertise in the new technologies sweeping the industry a decade ago led him to an array of leadership positions.

According to a statement that accompanied the Securities and Exchange Commission charges filed against him, Madoff served variously as vice chairman of the National Association of Securities Dealers, as a member of the NASD’s board of governors, and chairman of its New York region. He was also a member of the Nasdaq Stock Market’s board of governors and its executive committee, as well as chairman of its trading committee.

That credibility led scores of people -- many of them as sophisticated in the ways of Wall Street as Madoff himself -- to steer billions of dollars to him, apparently without ever questioning his methods.

“Everybody knew Bernie,” said Foerster. “Everybody knew the Madoffs in the business.”

According to Foerster, Madoff was recognized as a “market structure guy,” meaning his expertise lay in the arcane mechanics of how stocks traded.

“He was on the cutting edge,” said Foerster.

Among some Wall Street insiders, however, that regard did not extend to Madoff’s capabilities as a money manager.

But that didn’t seem to matter. People trusted him anyway.

I trusted him.

As a reporter new to the business beat in the late 1990s, I was bewildered by the rapidly changing landscape on Wall Street.

Stock trades, once negotiated almost exclusively by humans on the floors of venerable institutions such as the New York and American Stock Exchanges, were migrating en masse to electronic exchanges like the Nasdaq, and smaller platforms known as electronic communication networks, or ECNs.

Madoff had seen all of this coming for years, and he made a fortune with his firm, Bernard L. Madoff Investment Securities, which he founded in 1960 and ran with his brother, Peter, 63, and two sons, Mark, 44, and Andrew, 42, among other family members.

Employing the most sophisticated, state-of-the-art technology, Madoff Securities was a pioneer in creating smooth and speedy markets for huge volumes of stock trades conducted via computers.

Aware of his already legendary reputation, I called Madoff, hoping he might help me make sense of the seismic shifts taking place on Wall Street.

A few days later I was sitting in his office on the 19th floor of the Lipstick Building in midtown Manhattan as he patiently explained the complicated minutiae of trading -- order flow, fills and partial fills, stop orders, etc… -- and how these procedures were being affected by the rapid shift from humans to computers.

He seemed to have no agenda. He didn’t tout his own firm’s efficiency or reliability over that of his competitors. And he never bragged about himself.

Best of all, he took the necessary time to help me understand what he was talking about.

I used to stop by his office every now and then to catch up, and we spoke pretty regularly on the phone.

What struck me most about Madoff wasn’t his expertise in technologies that were transforming the securities industry, or his patience in explaining them to me.

What I remember was the obvious pride he took in the family-run business he had built. As he showed me around the trading floor, he stopped to point out his brother’s office, and went out of his way to introduce me to his two sons, both of them around my age.

In a twist worthy of Shakespeare, it was Madoff’s sons who reportedly turned him in after he had confessed to them that his house of cards had finally collapsed.

Madoff was once fond of saying, “The owner’s name is on the door,” clearly a reference to his belief that his firm was different -- perhaps more trustworthy? -- than the big conglomerates with whom he competed.

A week ago, the Madoff name was synonymous with a pioneering, seemingly impeccably run firm in a business not known for its strong ethics.

Now, given the scope of the allegations, the name will represent something else entirely -- and probably forever. That’s some legacy to hand down to your children.