For the investing world, the death of Bernie Madoff has been a reminder of Wall Street’s dark underbelly.

When stocks are climbing and returns are looking good, investors sometimes don’t ask enough questions. And when that happens, fraudsters can get away with stories that are too good to be true.

Take, for example, the often referenced “FOMO” trade — the fear that if you take too long to consider an investment idea, you’ll miss out on more gains.

Certainly Madoff investors didn’t want to miss out on what seemed to be clockwork-like returns from someone who at one time had about as much credibility as anyone on Wall Street.

For those who covered his downfall, it was clear that he was always ready with an answer to cover his tracks.

In fact, one could wonder whether his Ponzi scheme would have been exposed had it not been for the financial collapse in 2008.

He even leveraged the well-earned reputations of his own children.

At the time the story broke, I was a Bloomberg reporter based at the New York Stock Exchange. One of the many market participants I spoke to on a daily basis was his son Mark. I still remember the silence of not hearing back from him after his father’s scam made international headlines.

For all the suffering and tragedy that came out of Bernie Madoff’s web of lies, few seemed to take it harder than Mark, who took his own life two years later.

Bloomberg’s New York head office is just a few blocks from the duplex penthouse where Madoff originally returned on bail. For weeks, reporters and cameras camped outside his building, hoping for an answer to a simple question: Why’d you do it?

I’m not sure anyone ever felt they got the answers they craved. And eventually, the cameras moved along to other stories.

But for years to come, Bernie Madoff will be a reminder of what can happen to investors when they don’t ask enough questions.