When you've known someone for a long time (say, 9 years) and you hang out a lot (because you still love them) you start to provide a service to each other. That service being, acting as the other's overfill brain for random information, and if not able to provide the exact information, at least you can be a jumping off point for coherent thought processes. Example:
Tom: Who sings this song?
Me: I'm not sure...
Me: I don't know who that is.
Tom: Oh - nevermind. Cialis is that male impotency drug.