While the Federal Reserve continues to express concern that inflation is too low, David Rosenberg, chief economist at Gluskin Sheff + Associates, worries about an increase in inflation.

"Whether you are bullish, bearish or agnostic on equity markets, there is no greater complacency out there today than the outlook for inflation," he writes in Canada's Financial Post. "It may have spent a long time in a coma, but it’s far from dead."

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The consumer price index rose 2.1 percent in the year through May. But the Fed's favored inflation indicator, the personal consumption expenditures price index, gained only 1.6 percent in the year through April, 1.4 percent excluding food and energy.

But Rosenberg notes that gold prices hit a 2 ½-week high Friday and that copper prices are rallying.

"If you don’t see inflation, then you have been focused on hedonically-adjusted consumer price data: the markets for assets and commodities tell a different tale," he says.

Meanwhile, Rosenberg says the Fed will probably raise rates in the first half of 2015, earlier than many economists, who forecast an increase in the second half of next year.

Not everyone shares his concern about inflation. "Inflation in the U.S. is in a sweet spot. It’s not too hot, it’s not too cold," Millan Mulraine, deputy head of U.S. research at TD Securities, told Bloomberg News.

"The disinflationary stress that we’ve had over the past two or three years has effectively ended. That’s the big story here."

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