These are not problems with phone numbers. 20 years ago I knew all phone numbers from my friends and kept them on paper. I still keep them on paper. The points

These are not problems with phone numbers. 20 years ago I knew all phone numbers from my friends and kept them on paper. I still keep them on paper. The points you describe could also be said about e-mail addresses and website addresses. This is about people putting too much trust in (electronic) technology.