I'd love to institute the "one in, one out rule" in my house and am hoping to start on it very soon. Actually, in my house, I'd really like it to be one in, ten out. What this means is that when you bring something new into the house, you must get rid of one existing piece.
You can apply this to anything–clothing, home decor items, books, toys–it works with anything. There is always something in the house that you can get rid of. Of course, it will be slow going and it won't solve all of your clutter problems, but it shouldn't work to create more clutter either. Status quo is sometimes just fine.
Now do you see my point about one in, ten out?!