Money Pouring Into Stocks 'Is Usually a Negative Sign'

Despite all the ballyhoo over money flowing back into stocks, the return of mom-and-pop investors means little to how well the market performs this year.

Measuring fund flows—or the amount of cash going into mutual funds—is Wall Street's favorite new past-time when it comes to predicting market activity, and the bulls are gushing over the amount surging into equities to start 2013. (Read More: Dow Breaks 14,000 Finally; What's Next for Market)

But in the greater historical context, such moves can foretell very little.

For one thing, January almost always sees money coming to the market, and this year is no different.

For another, money is pretty much pouring into all asset classes except for some commodities, so it's hard to read anything into mutual fund trends at this point.

"When mutual fund investors pile into equities, it's usually a very negative sign for the market," legendary mutual fund titan Jack Bogle, founder and head of Vanguard, said in a CNBC interview Friday as the market staged a robust rally.

And piling in they are.

Stock-focused mutual funds saw about $32 billion in fresh cash to start the year, according to the Investment Company Institute, as the Standard & Poor's 500 posted its best January in 16 years. (Read More: January Barometer May Not Deliver This Time Around)

So it's all risk-on now, right?

Hold on a minute.

Safe-haven bond funds did even better than stocks, collecting some $37 billion in new assets. Dead money in zero-yielding money markets, meanwhile, was little changed near $2.7 trillion.

And it wasn't just stocks and bonds that saw piles of new money come in. Even funds that focus on bank loans posted a fresh new record last week, raking in $927 million to cap off a tremendous month that saw net assets grow by $3.3 billion.

In fact, bank loans topped every other asset class in new money as a percentage of total assets, according to Bank of America Merrill Lynch.

Taken together, the numbers indicate that the answer to whether the market is on risk-on or risk-off mode is "yes." (Read More: Why Inflation Could Eat Into Stock Gains: Kyle Bass)

That's likely one reason why fund flows are being treated with caution by some stock market experts.

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"Inflows are favorable for equities, but not assurance of continuous gains," Tom Lee, chief market strategist at JPMorgan Chase, said in a note.

"Consider the contra, equity outflows over the past four years certainly did not prevent the S&P 500 from doubling," he added. "Ultimately, in the short term, equity gains hinge upon favorable risk/reward relative to the consensus view."

The otherwise bullish Lee sees the current market getting a little toppy, with at least a short-term pullback possible because signs of enthusiasm are getting overheated.

He points to the American Association of Individual Investors survey, in which the bulls double the bears, 48 percent to 24 percent. The Investors Intelligence Survey, which polls newsletter authors, has the bulls ahead 54-22, around the same level at the last meaningful market pullback in September.

Lee recommended clients move to high-quality assets while the market churns.

Bogle pointed out that retail investors remained on the sidelines for most of the 120 percent market surge since March 2009, so a rush back in now could be worrisome.

"When retail investors think it's all blue skies out there, we could all too well be looking for a big pullout," he said. "It's very counterintuitive."