Online advertising has been booming, but according to The New York Times, its growth is threatened because nobody can get the basic visitor counts straight.

Big media companies are frustrated that their counts of web visitors keep coming in vastly higher than those of the tracking companies like comScore or Nielsen//NetRatings.

"You're hearing measurement as one of the reasons that buyers are not moving even more money online," Wenda Harris Millard, president for media at Martha Stewart Living Omnimedia, said. "It's hugely frustrating. It's one of the barriers preventing us from really moving forward."

A main source of the discrepancies is over how to measure internet use in the workplace. Online publishers say that the tracking companies' systems drastically undercount people who use the web during work hours, particularly in offices where corporate software makes the wanderings invisible to the tracking systems.

Some web publishers say the panels also lack representation from students on college campuses, Hispanics and other demographic groups.