In the 2007-08 flu season, Google accurately estimated current flu levels one to two weeks faster than published CDC reports in each of the nine U.S. surveillance regions, Google said in a statement.
This shouldn't be a big surprise when in the past, according to the same article, trends were determined by:
...physicians' reports of patients with flu-like symptoms, lab reports of influenza from nasal and throat swabs, and death certificates.
I suspect this will also send up early flags in the event of chemical or biological terrorist attacks as well.
Go Google! And kudos to the CDC for collaborating and seeing the potential in non-traditional epidemiology.