I give it at CVS because I never have my card. Ditto for Borders discount club.
Supermarkets don't ask.
Most of the rest of my shopping is online. Probably I have given those businesses my phone number, in the normal course of ordering.
I figure, my phone is for MY convenience. I choose not to answer it, most of the time.
When I forget my card and they ask for my number to look it up, I give it to them, but it doesn't work so I have to give them my cell and that still doesn't work, and then I say 'oh I must have given a fake number when I filled out my card". I usually get a look with that
