Google trends as forecast tool?

Hal Varian, Chief Economist at Google, claims that the huge volumes of data generated by Google Trends and Google Insights for Search can "help improve forecasts of the current level of activity for a number of different economic time series, including automobile sales, home sales, retail sales, and travel behavior". For example, if people start doing significantly more searches for "Real Estate Agents" in a certain location, it is tempting to think that house sales might increase in that area in the near future.