Websurfing Damaging U.S. Productivity?

Bert writes "Ars Technica does a good job of debunking a study that claims that American business lose $178 billion a year to web surfing in the workplace. Particularly alarming is the fact that the study used the beliefs of 350 IT managers to determine how many hours a week the average employee wastes online. Like the article asks: where's the calculation of how much time we all spend answer work e-mail at home?"