In April 2012 a London-based left of centre think tank, Demos, published a report; which I read and forgot to post here The three authors include Sir David Omand, one of Whitehall's respected intelligence guru's; which made it more interesting to read.

Link:http://www.demos.co.uk/publications/intelligence

The growth of social media poses a dilemma for security and law enforcement agencies. On the one hand, social media could provide a new form of intelligence – SOCMINT – that could contribute decisively to keeping the public safe. On the other, national security is dependent on public understanding and support for the measures being taken to keep us safe.
Social media challenges current conceptions about privacy, consent and personal data, and new forms of technology allow for more invisible and widespread intrusive surveillance than ever before. Furthermore, analysis of social media for intelligence purposes does not fit easily into the policy and legal frameworks that guarantee that such activity is proportionate, necessary and accountable.

This paper is the first effort to examine the ethical, legal and operational challenges involved in using social media for intelligence and insight purposes.
A "lurker" who works in this field commented:
a thoughtful analysis...they avoid that can of worms as they are keen to discuss the ethical / legal framework that would be needed to support this
The Frontline Club, London held a discussion evening after the launch, rightly the title was 'Cyber-snooping a threat to freedom or a necessary safeguard' and is available on a podcast:http://www.frontlineclub.com/events/...safeguard.html