For a profession that likes to think of itself as transparent, auditors might have some way to go. Particularly when it comes to companies revealing to the market why they have dismissed or changed an auditor.

According to risk researchers, Glass Lewis, it's one area that needs urgent attention. It's absolutely critical information for investors.

In their report Mum's the word, they point out that 1,430 publicly held companies changed their independent accounting firms last year including 77 companies that changed auditors at least twice. But in the vast majority of cases, we don't know why, because neither the companies nor the auditors disclosed the reasons.

"Perhaps it's our skeptical nature, but we suspect a lot of the companies that stayed mum changed auditors because of less virtuous reasons: to seek more favorable opinions, to flee from disagreements,to cut costs in a way that may diminish audit quality, or because their former auditors couldn't rely on them," says the report.

The report calls on the SEC to expand its list of required "reportable events" so that investors get more information about such matters as whether there had been difficulties conducting the audit and whether the auditor had advised the company about potential fraud.

Investors need nothing less from the profession that's required to watch over the companies that they, the investors, own.