It seems the UK Gov't have done the hard work in determining which scenarios are the most likely to happen and what impact they may have, no surprise there, however they have also seen fit to share it with the public, which was nice:

BBC News Article:
http://news.bbc.co.uk/1/hi/uk_politics/7548593.stm

The Risk Register Documents:
http://www.cabinetoffice.gov.uk/reports/national_risk_register.aspx

OIMO

Sometimes the gravest risks to "national security" come from within. Even John Major (of all people!) suggests that citizens of the UK face a risk that could devastate their society:

http://tinyurl.com/52sz87

or

http://www.timesonline.co.uk/tol/comment/columnists/guest_contributors/article4075503.ece

Henry, I fear you are correct, it is a sad state of affairs when the central cause for concern is the government and its reactionary responses.

OIMO