Sentiment analysis has plenty of research around it, and once you've got a big enough training and validation set, it can give very good results. My old boss wo

Sentiment analysis has plenty of research around it, and once you've got a big enough training and validation set, it can give very good results. My old boss works for a company that runs sentiment analysis on comments made about companies to automatically highlight positive/negative messages - it's not a massive leap from there to repurpose that to analyse positive or negative news reports about a company.