When one of Albert Einstein's colleagues asked the eminent physicist for his telephone number one day, he reached for a telephone directory and looked it up. "You don't remember your own number?" the man asked, understandably startled. "No," Einstein replied with a shrug. "Why should I memorize something I can so easily get from a book?"
[Though this story is likely apocryphal, Einstein did claim never to memorize anything which could be looked up in less than two minutes.]