How does whistleblowing help companies?

We are particularly interested in hearing from whistleblowers  and their representatives, those involved in Employment Tribunal claims brought by whistleblowers, and HR and Audit professionals who investigate disclosures.

Even if a whistleblower uncovers a scandal they may still be perceived as disloyal and unemployable, which is why anonymity is key. Requiring employees or others to blow the whistle can be dangerous because it can put individuals between a rock and a hard place, at risk of losing their job if they do or don't make a disclosure.  At the same time organisations struggle to understand whether a high or low number of disclosures is preferable.  The situation is complicated by the possibility of financial rewards for whistleblowers, and reputational risks for organsiations who discriminate against whistleblowers. These are just a few of the dilemmas, and the questions which arise seem endless. 

Is whistleblowing a safety value which companies should encourage, or are whistleblowers usually self-interested opportunists? How can we get the balance right? Is the Public Interest Disclosure Act fit for purpose? What is the best way for whistleblowing to evolve in the UK?  Please share your views and experiences.