The flow of information has become faster with the internet and surprises are factored in instantly. Few will argue that a surprise, both positive and negative, can violently move the price of a security. After reporting earnings that were below expectations on 15-Feb, Abercrombie and Fitch fell from 24 to 15. Even though these are but a few examples, it is obvious that new information can move the price of a security. Many academics also argue that price movements are largely random and only influenced by the introduction of new information.
Many academics do acknowledge that some drift exists in security prices, but never a trend.