Katherine Heigl recently told US Weekly that she didn't know her own phone number; "It's all in my iPhone!" she explained.
While a few years ago, I would have thought that was crazy, I have to admit that I actually don't know my work phone number or my house line. My excuse is the same as Katie's; I may not know them off the top of my head, but they're in my cell phone.
These days, I only know a handful of phone numbers by heart, like my main cell phone, my boyfriend's cell, and my mom's house line (because it was my phone number for years). I'm always trying to memorize more phone numbers for emergency situations, but I'll always think of my cell phone's contact list as a crutch. What about you?