My wishlist is growing exponentially since I started browsing my friends' pages on aNobii. It works better than the usual "spookily accurate" recommendation systems you find on shopping sites, because your friends' ratings carry much more weight than the simple act of buying an object (which is over-rated by bookshops, since they often don't have actual feedback).
I guess aNobii tries to make its money acting as referral from those same bookshops, I wonder how much they actually make. It would be really powerful if they allowed people to have their own referral ID embedded in "buy" links, so that I make money if my friend buys a book I recommended. I guess that, for this to really happen, Amazon should buy out aNobii (a small Hong Kong startup, from what I understand) and possibly rewrite it from scratch, but it would be a fantastic move.