I can understand that some may not want to reveal personal information for obvious reasons. However, there are so many ways to get around this (provide board handle, reference, meet in a public place beforehand..etc). For those providers who want to be sure that the client is serious, if dealing with outcalls, have the client arrive at the hotel early and then call from the hotel with the room number. Knowing his room number, the SP can then call him back to be sure he’s really there.
One more thing. To those who freely give out their cell phone numbers, they may as well also provide their real names. I have caller ID at work and it will display the name of whoever is calling including someone calling from a cell phone. The only way to hide your name and number is to block your number prior to calling. In fact a friend of mine also has caller ID on his cell phone. Whenever his sister calls from the cell phone which she shares with her husband, her husbands name pops up since the number is officially registered under his name.
So in summary, to those concerned with privacy issues, DO NOT give your cell phone number. It’s equivalent to providing your name. Remember that this is 2018.