I remember when mobile phones first started to become common place one of the wiz bang new things that they enabled was the ability to store phone numbers in the phone itself. Suddenly phone books were so yesterday and we all became so reliant on our phones for phone numbers and addresses. Two problems were created by making all our contacts mobile. 1. Our ability to memorise numbers is failing and 2. more importantly it became a huge drama whenever something happened to our phone and we lost all our contacts!
These days the cloud has given us all the ability to instantly back up all our essential contact information through whatever cloud service you prefer.