As much as I dislike yahoo, Google is not a company to trust. Consider the release of Google trends and you will understand that they did not release data on their own sites.
While Techcrunch provides an explanation, most likely Google has the data and regulators would become concerned they are controlling the Internet.
A comment on Techcrunch is more accurate, why demonstrate to the world that Google controls the traffic?
On a tangent, enter the phrase Microsoft or spam or Software and you'll see a decrease. Now enter "online movies" and see a huge increase.