[SEJeff]

Using sentiment analysis. In fact, there are some traders (crazily!), which do just that.

http://www.wsj.com/articles/tweets-give-birds-eye-view-of-st...

http://tradethesentiment.com/

[notahacker]

An algorithm parsing the aggregate reaction of mostly non-experts, mostly to news delivered over relatively slow mainstream media channels, is going to be much slower than a human hearing the investor briefing and hitting the "sell at any price" button.