Maybe close to anonymity - that it's easier now than ever for groups of people with common interests to communicate and form communities, and easier than even to ignore those physically around us. At the same time, increased ease of travel and the globalizized economy brings vastly different cultures together. These two things combine to create strong and polarized groups with completely different goals and values.

Add the icing of media that makes money from stirring up problems, and you have continual chaos.