Magic number.

Even large mutual fund companies find themselves disclosing the names of their wealthiest accountholders. American Funds, owned by Los Angeles-based Capital Group Cos., manages more than 30 mutual funds with $300 billion in assets. Though most large shareholders are institutions, occasionally an individual investor may hold more than 5 percent of a fund.

American Funds spokesman Chuck Freadhoff said the company has to comply with SEC regulations and list any shareholder whose holding exceeds the magic number. "Not complying is not an option," he said.

If the shareholder is an individual investor, Freadhoff said the fund only lists the state the investor lives in, not the street address. (If it's a business or a pension fund, then American Funds lists the street address.)

"We work strictly through financial advisors, and we work very hard to make sure financial advisors are aware of all the roles that will impact their clients," Freadhoff added.

But even financial managers find the disclosures alarming.

"I'm surprised that mutual funds give that sort of disclosure," said Hal Harley, managing director of Deutsche Bank Private Wealth Management Group in Los Angeles. Harley's group manages high net worth individuals where privacy is "absolutely paramount."

Neither CNI Charter Funds nor American Funds could say whether individual investors were informed of their inclusion in the SEC filings.

Some wonder whether the 5 percent rule should even apply to a security like a mutual fund. Classes of shares often serve simply to separate different fee structures within the fund. Some investors prefer to pay mutual fund fees when they purchase shares, while others like to defer fees until they redeem shares.

Different classes in the same fund hold the same investments, so there is a question as to whether 5 percent of a particular class could really impact the overall value of a fund's shares. The SEC is reportedly looking into all of these issues, but Heine could not confirm if any changes were imminent.