Head and shoulder patterns are always valid - you just want to assess the probabilities of them playing out by considering other patterns and indicators. I keep a very open mind to these patterns actually PREDICTING all the events you listed above (hack, sf fail, etc) - trading stocks is all about information, and it seems logical to me that the buying and selling patterns on a chart would indicate investors who know more than we do making their moves. But when it comes to head and shoulders patterns I don't give them a ton of weight unless other factors confirm them because all traders know about them and all see them--but to ignore them is a very dangerous game. Hope that helps.