Knowing current location of anyone is the most crucial part. Big tech firms or companies do involves in many cases. Normally mobile phones communicate nearby cell phone towers so your telecom provider knows where you are calling or texting. That these companies sell data to the local enforcement cells. Based on the research done by digital forensic expert of International Institute of cyber security shows on how a researcher named Joseph Cox gave a phone number to Bounty hunter for searching its current location. Bounty hunter agree that he can find current location of most phones in USA. Later on bounty hunter sent those numbers to his own contact who would track the phone. The contact responded with the screenshot of the Google maps containing longitude and latitude. All location have been traced without deploying any hacking tools or any previous data of target.
Ethical hacking researcher of international institute of cyber security shows how mobile devices verification companies are selling location data to anyone without asking for any warrant or law enforcement verification. Getting an location by just paying $300 have become so easy that any person can become stalker.
All those information below from Microbilt shows that companies are using different methods to sells information to local landlords, vehicles salesmen, bounty hunters and some potential renders. The most of the work is done through word of mouth networks and special marketing ways to tell people that we do mobile device verification services.
Companies like Microbilt (http://www.microbilt.com/category/identity-verification) and
And below is service agreement to monitor user location using LBS (Location Based Services)
Securus (https://securustech.net) sell location of any user. But these companies works only with the involvement of middlemen. Some earlier research shows that these services are used by bounty hunters for non-commercial purposes like tracking their girlfriends. Another source shows that microbilt buys access to location from another company called Zumigo (https://zumigo.com/) and then sells that data to large no. of companies like Microbilt.
LocationSmart another location gathering company faced harsh criticism for selling data using LocationSmart. LocationSmart was selling data using buggy website panel which means anyone could geolocate phones in USA by just click of a mouse. Securus company which provides phone tracking to low level enforcement without asking for warrant.