More than a fair share?

Why fear what the intelligence services know about you when you're already giving it away on Facebook?

Social media have been in the news this week thanks to revelations that the US National Security Agency has harvested vast amounts of data from telephone calls and online sources.

Professor Tim Wu of Columbia Law School even suggested in an interview with the Wired magazine website that we all stop using Google and Facebook if it's proven that those companies have been collaborating with intelligence agencies.

But it's not quite as simple as that, because many of us have been happily giving away our personal information for years. A University of Michigan study reveals that Facebook and Twitter are magnets for narcissists - people who willingly and constantly broadcast their opinions and activities, and post pictures of themselves ("selfies").

Some members of the "quantified self" movement go so far as to use wearable technology to register precise details of their bodily functions - and lovingly report them online. The choice is yours. If you don't want the world know what you're doing, don't shout about it online.

If that's too hard, then perhaps Facebook should - as some online commentators have already suggested - change its posting options menu to include a "Share with the CIA" feature.