Salary.com has a great article called Wasted Time At Work Still Costing Companies Billions in 2006. From the opening paragraph:
the average worker admits to squandering 1.86 hours per 8-hour workday, not including lunch and scheduled break-time
Amazing, but it gets better:
The biggest distraction for respondents was personal Internet use. 52.0% of the 2,700 people polled cited web surfing as their #1 distraction at work. Socializing with co-workers came in second at 26.3%. Conducting personal business, “spacing out,” running errands, and making personal phone calls were the other popular time-wasting activities in the workplace.
I particularly enjoyed the “spacing out” time waster. It came in at 6.6%.
The sum of all this wasted time . . . $544 billion (yes, with a “b”).