Baskets?

I’m rolling along with GTD–at work I’ve gone through my initial collection to IN and then recycled, trashed, and filed just about everything (except a pile of stuff in a spare office that needs to be archived). I’m using Things.app as my task-management organizer.

Simple question: do you all use desk baskets? If so, how many and what for? I have a mailbox in the front where all my office mail/documents arrive. Do I need stuff on my desk as well?