Analysts and commentators are often derided for saying that stocks are overpriced and due for a correction. Behavioral economics, the fad at the moment, holds that making predictions is like throwing darts at a dartboard with a blindfold on.

But what happens when a growing chorus of the best investors in the world all start to say exactly that? Should these people also be treated like Greek mythology's Cassandra, who could see the future but couldn't persuade others about her predictions?

The latest example is the chairman and CEO of Goldman Sachs (NYSE:GS), Lloyd Blankfein. At an industry conference this week, Blankfein expressed concern about the current state of the markets, saying that the situation "unnerves" him.

"Things have been going up for too long," he said. "When yields on corporate bonds are lower than dividends on stocks? That unnerves me."

Goldman Sachs chairman and CEO Lloyd Blankfein (center) with the investment bank's co-presidents David Solomon (left) and Harvey M. Schwartz (right).

Goldman Sachs Chairman and CEO Lloyd Blankfein (center) with the investment bank's co-presidents, David Solomon (left) and Harvey M. Schwartz (right). Image source: Goldman Sachs.

The head of Goldman Sachs, which has been among the most omniscient of trading firms on Wall Street in recent history, adds his name to a growing list of other high-profile financiers that have publicly expressed concern.

Here's what Howard Marks, co-chairman of Oaktree Capital Group (NYSE:OAK), wrote in a memo to clients in July:

[I]t's essential to take note when sentiment (and thus market behavior) crosses into too-bullish territory, even though we know rising trends may well roll on for some time, and thus that such warnings are often premature. I think it's better to turn cautious too soon (and thus perhaps underperform for a while) rather than too late, after the downslide has begun, making it hard to trim risk, achieve exits, and cut losses.

Since I'm convinced "they" are at it again -- engaging in willing risk-taking, funding risky deals, and creating risky market conditions -- it's time for yet another cautionary memo. Too soon? I hope so; we'd rather make money for our clients in the next year or two than see the kind of bust that gives rise to bargains. (We all want there to be bargains, but no one's eager to endure the price declines that create them.) Since we never know when risky behavior will bring on a market correction, I'm going to issue a warning today rather than wait until one is upon us.

Here's Jeffrey Gundlach, co-founder and CEO of DoubleLine Capital, a fund with $110 billion in assets under management:

If you're waiting for the catalyst to show itself, you're going to be selling at a lower price. This is not the time period where you say, "I can buy anything and not worry about the risk of it." The time to do that was 18 months ago.

Here's Warren Buffett, the chairman and CEO of Berkshire Hathaway (NYSE:BRK-A) (NYSE:BRK-B), intimating the same thing in a letter he penned earlier this year to the shareholders of Berkshire Hathaway:

Every decade or so, dark clouds will fill the economic skies, and they will briefly rain gold. When downpours of that sort occur, it's imperative that we rush outdoors carrying washtubs, not teaspoons. And that we will do.

And here's Ray Dailo, the co-founder and chief investment officer of the world's largest hedge fund, Bridgewater Associates, writing recently in a LinkedIn post:

When it comes to assessing political matters (especially global geopolitics like the North Korea matter), we are very humble. We know that we don't have a unique insight that we'd choose to bet on. Most importantly, we aim to stay liquid, stay diversified, and not be overly exposed to any particular economic outcomes. We like to hedge our bets, though we are never completely hedged. We can also say that if the above things go badly, it would seem that gold (more than other safe haven assets like the dollar, yen, and Treasuries) would benefit, so if you don't have 5%-10% of your assets in gold as a hedge, we'd suggest that you relook at this. Don't let traditional biases, rather than an excellent analysis, stand in the way of you doing this (and if you do have an excellent analysis of why you shouldn't have such an allocation to gold, we'd appreciate you sharing it with us).

In short, one can be as dogmatic as one likes about predictions, but when investors and financiers like these start expressing concern, it's probably not such a bad thing to listen.

John Maxfield has no position in any of the stocks mentioned. The Motley Fool owns shares of and recommends Berkshire Hathaway (B shares). The Motley Fool recommends Oaktree Capital. The Motley Fool has a disclosure policy.