"We’re in the midst of a boom in devices that show where people are at any point in time," the New York Times reports. The devices – cellphones, mostly – not only show people where people are (as in parents tracking kids) but also show advertisers where people are. In effect. Cellphone users can opt to allow the information about their location to inform software in the phone what advertising would be relevant to the user at that moment. Groups have raised consumer privacy issues, and providers of the ad-targeting software (at least some of them) seem to be factoring those concerns into it. With one such product, CitySense, users opt in (e.g., for ads that tell them where everybody's going for pizza or music near them) – and "opt in" means it isn't there by default – to the service and "if they want to purge their data, they can do so at any time," according to the Times.