‘It’s Going to Collapse’: 5 Scary Stock Market Predictions From Smart Investors

Stocks have been trading at or near record highs -- but not everyone is so certain that the acceleration will continue.

One measure of optimism, fund flows, showed a reversal last month, with fund investors -- a group that largely consists of middle-class American retirement savers -- pulling more than $2 billion net in May from domestic stock mutual funds and ETFs.

Many professional investors are expressing concern as well.