the importance of a clients feedback?

[sarahxxx]

I am still much of the Old school way of doing business

I advertise with a telephone number, people call me, make a booking and turn up. I have no idea who they are, where they come from or if they are good or bad clients.

It worked really well before the internet and it still seems to work just as well for me. how selective do I need to be? I would guess those that are would not advertise a telephone number as there would be no way of checking who the person calling was, nor would they have a web site or advertise through other publications etc as they would have no way of checking on the clients feed back.

Sarah