If you mean what I think you mean I think that is unworkable for most of us. Drop your car off at the shop for some work. Mechanic calls you from his cell phone because it's handy and the shop line is tied up. You never get it. Or school nurse calls you about an emergency. Neighbor calls you to tell you your dog got out from the back yard. That kind of stuff is about the only reason I have voice service - I don't use the damn thing to talk for the most part.

I do mean what you think I mean, and I understand what you're saying, but if the sort of volume of spam people are talking about became the norm, for me it would be either white list or stop owning a phone at all. Between those two options, white list seems the better one.