"Successful promotion of a scare requires that some interest group benefits. Sometimes this is the scare-promoters themselves. Scientists have learnt that exaggerated claims are a route to a media profile and research funding. There is little downside in predicting disaster: if it does not materialise they can claim to have been instrumental in staving it off. Scares that thrive, such as the millennium bug and swine flu, have commercial interests that benefit from their propagation. Naysayers in the credit boom, by contrast, were trampled in the rush to share the riches available to those who denied or disregarded the dangers."
In a nutshell.
"The political and regulatory incentives are either to downplay risks or exaggerate them – or to do each at different times."
- http://www.johnkay.com/2010/04/21/how-our-leaders-get-to-grips-with-a-scare-story/ (view on Google Sidewiki)