Depends on how data-nuts they can actually go. If they wanted to get really nuts and they actually stored all the data they can track, from your house, car, phone calls, etc... think what any extremely intelligent and powerful (i.e. resources– ATT or NSA, doesn't matter) could do with that kind of information. If enough people subscribed and they could start plugging in external data such as sex offender registrars, it would only be a matter of time before they found a decent model for pattern behaviors. When there's a crime in the area or someone is suspected of X, they could simply compare their base model to John Doe's log, timestamps and all, and determine that hey, those 5 phone calls and 3 garage exits in one hour do seem fishy to us! *knock knock

The good: That's a lot of work for anything that isn't "major" crime. I can't imagine it would help them any more for cybercrime either. BUT, it would be super interesting to see such a system implemented if you're never on the receiving end...

The bad: Everything else. Regardless of how advanced it is, how they use it is everything. And given their track record (sourced above), privacy/trust doesn't seem to be their forte.