This is naive. Via triangulation they know your approximate location, and there are likely cameras with facial recognition and/or license plate readers in the area that can be used to correlate with arrival/departure to get your identity. Unless every single thing you use is in somebody else's name and you wear some kind of disguise everywhere it is already possible to bypass anonymity in most urban areas. If someone isn't doing it already someone will be soon, there's a lot of money at stake.