There could also be trouble win big emerging market cities where the rising expectations are about to be disappointed, he said.

(Watch: Violent Riots Break Out Across Brazil)

Protests have already begun to spring up in Brazil. "The economy has been doing less well of late," Ferguson told CNBC. "Young people have got used to rising living standards, inequality has been coming down somewhat from its extraordinary terrible heights. And now as the economy slows down the frustration boils over because people's expectations were rising and now they're disappointed."

(Read More: Analysts Debate Appeal of 'Sour' Brazilian Stocks)

China also bears watching. Ferguson said he spent April in China and said the government is worried about social unrest. "The leadership are really seriously worried about the possibility of revolution," he said. Ferguson's host in China told him that some of they country's leaders are reading Toqueville's "Old Regime and the Revolution."

"They think they're 18th century France," Ferguson said.

"But my guess is they have better handle on this than their counterparts in Brazil," he added. "If there's one thing the Chinese communists do pretty well, it's public order. They run a pretty efficient police state."