The summer is over, complacency is dead, and markets are fun again

Global markets are great again!
On Friday, after more than 40 straight days of the S&P 500 closing inside of a 1% range, markets are selling off as the meme of the summer dies a quick death.
Complacency, the dominant theme in markets for the two months since the June 23 Brexit vote in the UK, has felt as though it's been the only theme in markets. And now, it seems, this is over.
Near 2:30 p.m. ET on Friday, the Dow was down over 300 points, the S&P 500 was down 43 points, and the Nasdaq