Just read an article sited on Silliman's blog about culling your books.
I have the WORST time getting rid of books, and I try to always at least GIVE them away-
The author, Scott McLemee has this to say at the end (one of my favorite quotes):
This might be the right time to adopt the outlook of Mae West. A friend asked her what she wanted for her birthday. “Just don’t get me a book,” she replied. “I’ve already got a book.”