The Institute of Psychiatry at the University of London conducted clinical trials with volunteer office workers to measure how a constant flow of messages and information affects a person's ability to focus on problem-solving tasks.
Participants were asked first to work in a quiet environment, and then while being inundated with e-mail, instant messaging and phone calls. Although they were told not to respond to messages, researchers found their subjects' attention was significantly disturbed.
Instead of boosting productivity, the constant data stream seriously reduced the volunteers' ability to focus. The study reported that an average worker's functioning IQ falls 10 points when distracted by ringing telephones and incoming e-mails, more than twice the four-point drop seen following a 2002 Carleton University study on the impact of smoking marijuana.
Professor Hugh Heclo of George Mason University observes: "In the long run, excesses of technology means that the comparative advantage shifts from those with information glut to those with ordered knowledge, from those who can process vast amount of throughput to those who can explain what is worth knowing, and why."which I think does rather illuminate the problem.
The second link, from the Juice Analytics blog, talks about the other side of the same coin - what to do with all this information, and they link to the amazing We Feel Fine project. All I can say is, load it and see for yourself.