I'm a librarian who loves anime, manga, and reading a wide variety of genres.
I plan to keep track of the amount of shelf space I free up (with donations or selling stuff to used bookstores) vs. the amount new purchases take up, starting today. I have no idea how long I'll manage to keep this up, but I think it'll be interesting (or possibly horrifying) to see how the numbers work out. Naturally, e-books will have no effect (hurray).
Today I donated 5 5/8 inches (sorry to you metric folks) worth of stuff to my library. Which is not a lot, considering that there's a used bookstore shopping trip in my near future.