Can you really trust the piracy damage claims?

A report on CNet on the trial of Pirate Bay has several interesting facts:

One of the most difficult tasks for companies that sell copyrighted music, movies, or computer software is estimating how much money they lose due to piracy. So they have been known to--how to put this delicately?--exaggerate.
[...]
The music industry's statistics have been called into question before: a 2006 government report obtained by The Australian says copyright owners "failed to explain" how they reached such dire conclusions. A report by the Organization for Economic Cooperation and Development found that losses due to counterfeiting and piracy are much lower than estimated by business groups. (In a related industry, The Economist has assailed software piracy statistics.)