"We found that mental performance, the capability of the brain, was also reduced. Workers cannot think as well when they are worrying about e-mail or voice mails. It effectively reduces their IQ".
The Internet is in effect a denial of service attack on our brains. Constantly hit with new useless information we literally can't pay attention to other parts of our life. The internet may not have the same kick as cocaine, but the internet makes up for its lack of single dose potency by having an infinite, constant, and varied supply.