As the Times looks at the story of a man who couldn't call his girlfriend after his cell phone was stolen because he didn't know her number, they note that the only number many cell phone users know by heart is "867-5309." As one man in his mid-20s put it, "As soon as high school came around, your friends got cellphones, and you stopped remembering their numbers." So, is your iPhone the only thing that knows all your friends' digits, or are you happy that you could at least remember your boyfriend's number that day you left your cell phone at home? (Not that we're speaking from experience or anything.)