But if the technique in question was promoted as a scientific means of doing just that, then you have to question it, and its proponents. LTCM is the example that springs to mind.
Yeah, but when everybody tells you to invest while the market is about to break down then there must be something wrong with the model.
In general I don't think it is the economists who tell you what stock to buy.
No "what" stock but that you should invest instead of a warning that the economy will break down soon. Most economists (something like 99,9%) failed to do so.
If all of the economists say that economy will break down next Monday, guess what? People will sell stocks in hand, and the economy will go down indeed, besides what is in truth. Since people are adaptive, they make decisions according messages they collected.
It's the job of economists to predict stuff like that to actually prevent it.