The efficient market hypothesis has a weak form and a strong form. It is well known (and acknowledged) that the strong form of the efficient market hypothesis does not hold (that all known information is reflected in the trading price of a given stock at any point in time).

Weakened forms of the hypothesis are that the market tends towards the price at which all information is incorporated in the quoted price, or that shares that are traded more frequently (the BPs and Vodafones) have more information incorporated into the price, but less liquid stocks tends to be less well researched.

Whether technical analysis works as a determinant of actual future value is no longer provable, as the existance of sufficient numbers of technical analysts actively trading on the market makes it a self-fulfilling hypothesis. If sufficient numbers of traders believe a kink followed by a hop followed by increased volumes means sell, then they will all sell at once and the price will fall, thus making them the cause of their own prediction.