Google have done a little bit of work predicting your likelihood of catching the Flu if you live in the US. They have tracked search terms and found that queries on the Flu can allow them to predict outbreaks two weeks faster than existing systems.
In itself this is quite interesting - but what else could they track? Political affiliation in an upcoming election? Predict share price fluctuation in specific markets?
If I was a betting man I'd quite full access to their data - however I suppose google trends goes somewhere to this effect - however not with this granularity of geography.
Have a look here