In sports, when a whistle blows it means it's time to stop — it's the end of the period or someone has committed a foul. Similarly, a whistleblower pipes up after something has gone wrong. Whether it's fraud, theft, or gross disregard for public safety, a whistleblower will make these misdeeds known to the authorities or the public at large.

Though many laud whistleblowers for their commitment to truth, others vilify them as nothing but grown-up tattle-tellers. And being a whistleblower is not without risk — many of the men and women listed here have paid ghastly prices for speaking out…