I would say it's more than a hope. Any trader whose strategy is closer to optimal will have larger profits over time and come to own a larger and larger fraction of the market. Though saying that out loud makes me realize optimal doesn't have to mean buying and selling according to true value. Optimal would in fact be predicting the behavior of other participants and trading off those predictions. I still think certain events ground value though: bankruptcies, mergers, and dividends attach a real cost/gain to holding a stock.