Consider the case of finding a set of strategies governed by a particular set of parameters in a book. For instance, the Moving Average lookback period. You will see authors posting certain strategies, albeit without revealing the market/time series with which they're carrying them out on or which exact parameters they use. This is the critical information, but it is also relatively straightforward to trial/test, assuming you have the available data.
Also - the same strategy, implemented identically, can be both successful AND a failure for two different traders with identical starting capital. Why? Because one may not have the stomach for a 50% drawdown in the equity curve, despite the fact that had they waited, a "big swing" would have been around the corner. It is as much about preferences/tolerances as it is about the actual rule set.
"A quantitative hedge fund only needs two members in order to be successful. A quant trader and a dog. The quant trader is there to feed the dog. The dog is there to make sure the quant trader doesn't touch anything."
* owns their own private jet/yacht/other signs of opulence
* didn't share it with anyone else
try to ignore it
What if they got their private jet by tricking others into following the strategy?
He realised he was observing the upper tail of a distribution of people who were aggressive risk takers, yet naïve about the risks they were taking – the businessmen one sees in the casinos are the ones successful enough to have enough money to lose.
These same people provide the underlying dynamics of capitalism. They are not rational, they do not understand risk and are therefore prepared to take risks that a rational agent would not take. And it is these people who drive the growth of the economy.