This is discussed all the time - there's a running joke about how the 200 day moving average only works because everyone believes it does. That said, there are

This is discussed all the time - there's a running joke about how the 200 day moving average only works because everyone believes it does. That said, there are so many different TA techniques / indicators / gurus that, for all but the most well known TA indicators (there are easily hundreds!), there simply aren't enough people trading on the signals at the same time for the same securities with enough volume for there to be a proper feedback loop. If there was a repeatable, predictable feedback cycle, it follows that we'd all be charting it and trading off it (or backtesting with quant analysis to confirm the existence of the cycle, or having long conversations about nothing and convincing ourselves it was fundamental analysis, or whatever your preferred method of analysis is.)