A University of Melbourne study showed that employees who surf the internet for personal reasons at work are more productive than those employees who do not. Click Here for the reference article from Yahoo!
The basis for this finding is the belief that short breaks during the day allow the mind to rest and re-focus, which increases concentration. The occasional break (also known as Workplace Internet Leisure Browsing or WILB) is something to ponder, as there are many companies out there spending considerable sums of money to ensure that their workers are not playing games, visiting social networking sites or shopping on the Internet during work hours.
Obviously employees who spend more than 20% of their work day on the Internet are not going to be as productive as those who do not, but a moderate amount of Internet surfing may not be a bad thing.