Research shows that employees are more apt to report fraud or other wrongdoing in the workplace when they know that whistleblower protection exists, says Northeastern University accounting professor Charles Bame-Aldred. An abstract of the study he helped conduct indicates, in part:

In the presence of protection, the influence of retaliation disappeared, as whistleblowing was perceived equally likely whether retaliation was threatened or not.

That's part of the reason legislators included the whistleblower provisions in the Sarbanes-Oxley Act of 2002.  But many of those who blow the whistle and then seek that protection after their employers do retaliate don't have any luck actually getting it. Former Cardinal Bancshares CFO David Welch is the most obvious example, since his case ended recently, but there are plenty of others. (See here for one.) In fact, a survey conducted in 2007 by researchers at the University of Nebraska College of Law revealed that only 13 of the 361 whistleblower cases heard by the Occupational Safety and Health Administration were resolved in favor of the employee.

But the fact that Sarbanes-Oxley's whistleblower provisions are weak at best doesn't mean that no one ever gets anywhere. As recently as June, a U.S. district court in Florida found that a former Best Buy employee's case could be heard in federal court. It doesn't guarantee success, of course, but it's further than most whistleblowers have gotten in the past.