Paul Graham, author of On Lisp, wrote an excellent article on having too much stuff.
And unless you're extremely organized, a house full of stuff can be very depressing. A cluttered room saps one's spirits. One reason, obviously, is that there's less room for people in a room full of stuff. But there's more going on than that. I think humans constantly scan their environment to build a mental model of what's around them. And the harder a scene is to parse, the less energy you have left for conscious thoughts. A cluttered room is literally exhausting.
At the Fincher household this article initiated a three day cleaning frenzy which has been refreshing. I've always complained our house doesn't have enough storage space, but see now that we just have too much to store.