Outside Mumbai domestic airport (this is where domestic flight take off and land unlike international airport .. also it is same airport but different terminal .. I digress) there is a taxi stand .. you stand in the line and one by one cabs (and auto rickshaws) will come and pick you up

Before you get on one of these cabs .. there are two airport officials (or contractors) who make you write your name and phone number and destination (in the name of accountability or security)

I am 90% certain (through grapevine) that that data is sold ..