There are specific limits on the quantity of certain items I can have: Six bars of soap, two bottles of lotion, four tubes of toothpaste, four deodorants, two toothbrushes, three photo albums, twelve CDs, ten books, and two magazines.
Imagine if that was all you could have. For someone like me who writes a lot and reads a lot, I tend to accumulate good books and every time I move I'm forced to give some away.