We've already seen the rise of angry protests in the Tea Party movement and Occupy Wall Street. All that is missing is violence, and it doesn't take much to trigger that.
Additionally, scientists have analyzed historical trends, and determined that social violence is cyclical, and that we are on the upwards trend in one fifty-year cycle. They even go so far to predict that 2020 will be the year of peak unrest. That's just around the corner. Http://tofudebeast.Tumblr.Com/post/53407508260/is-human-unrest-cyclical
The failures of American government only make this more likely. The rise of a surveillance state, distortions of our government by Big Business thanks to the inability to pass real campaign finance reform, the lack of a single-payer healthcare system. The government can only groan under the weight of special interests for so long before the people explode.
America is reaching a boiling point under the most corrupt president in U.S. History. Endless recession, record deficits, high taxation and unemployment, unequaled secrecy, amnesty for millions of illegal invaders, complete loss of privacy, the dismantling of the Constitution, a nation completely and intentionally divided by a man who would rather see America fail than to see Democrats not succeed. If this continues I not only see mass riots in the near future but actual civil war.
I'm at both yes and no for this one. People are too lazy to even work out or become healthy now in days, what makes people think we actually care what happens to taxes and the government? I think to bring good change in (and that's not to say it wont ever happen, because there are still people that care in the United States,) just saying that we would have to be willing to accept changes environmentally in the way we treat each other first before we make significant changes elsewhere. People are so closed to change even now, that might be too big of step, even then a riot wont change anything, all it will do is fuel violence and more hatred, all a riot is, is just that a riot. You actually get somewhere when you start actually thinking of plans to make the economy better. Just my two cents though.