I would highly recommend "Our babies, ourselves: How biology and culture shape the way we parent," by Meredith F. Small for anyone interested in learning more about this topic. It was fascinating! It discussed parenting in different cultures and one of the topics was co-sleeping.

I wish the book had been more neutral (the author tried, but you could tell which "side" she was on) but it did contain a lot of really interesting information. Based on what I learned through the book (and consequently through other research), I have decided to co-sleep with our baby, albeit in a bed right next to ours (you can buy co-sleepers that attach to the bed) simply because I would be afraid of squashing the baby and I don't think I'd get any sleep thinking about the possibility of it.