I have been reading market wizards interviews and it seems like with improvements in market data and professional traders across banks and hedgefunds squeezing out casual investors, hedgefunds have been struggling to find those same returns that they used to. When you discover a strategy or opportunity that works in a market, it's only a matter of time before that opportunity gets traded away as the market becomes more and more efficient with your.
Are potentially lucrative opportunities in the market still out there? Do markets constantly need people to reinforce efficiency, hence creating more or less permanent roles and opportunities(i.e. if traders are not around to trade a strategy/pattern/, do those opportunities return)?