With anxiety about hedge-fund woes gripping the market, funds have their own fear: their investors.

Some investors, particularly what are known as "funds of funds," are demanding their money back and may ramp up requests in the weeks ahead. That has prompted hedge-fund managers to sell securities to raise cash.

"As the hedge fund investor base broadens, hedge fund portfolio management...slips out of the hands of the portfolio managers and into the hands of the investors," wrote Andrew Redleaf, who runs Whitebox Advisors, a Minneapolis hedge fund with about $5 billion under management, in an August client letter. "It is no insult to the investors to say that this worsens performance."

Funds-of-funds select hedge funds on behalf of pension funds, wealthy individuals or other investors, and charge a layer of fees on top of the hefty fees levied by hedge funds themselves. They often ask hedge funds for the option to redeem money as often as monthly and get good terms because they can bring in big chunks of cash at once.

Some put in withdrawal notices to keep their options open, though they may ultimately decide to leave the money.