Dont Write Down Feature Requests

This is one heuristic which can work for filtering feature requests, but three places where it would fall down immediately come to mind:

1) You have a big customer who has requirements A through Q. Do you want to trust yourself to keep it all in your head?

2) You get 8 requests via email for features in area A of the product while you're really busy, then at a conference a week later you get 2 requests for something in area B from actual people who are standing in front of you. One of them is cute, and you are not Data. Without writing these down, do you think your brain will prioritize effectively?

3) How do you divvy up who works on what features if you don't write them down?