If you don't care about babies or human instincts, you can skip this post.
The Ferber fascists are strident. They're also wrong. Their explanation is you are training the baby, by gradually lengthened crying, to sleep through the night by themselves. However, this is a baby, not an adult human. They're giving the baby a lot more credit for understanding the message they are trying to impart (more on that later) than most adults would deserve. You know why a baby cries when it is left alone? Same reason a baby bird or dog does, it's afraid it's going to be abandoned forever.
And why the hell do they think it is so important for an infant to sleep alone? You get some Freudian explanations from most of them: Freudian justifications tend to give you more, unwanted, insight into the person using one than the subject. Do any of our primate relatives make their babies sleep alone? What about mammals in general? Oh, but we are different. No, we really aren't, least of all for an infant. It's worth noting that most cultures do not have such stupid parenting ideas, and their kids are better served by them. Ferberizing your baby gives the baby the same message as buying them a nanny while you stay at work, and sending her - the kid's real mother from the kid's experience - back to the Philippines when you're done with her: the kid is not a high priority.
Trust me, putting the kid in another room is not going to get you more sleep: you have to get out of bed and go down the hall to feed him. Mind you, if you have him completely traumatized so that he's learned to stay silent all night so no predator gets him during his abandonment... You think you're going to get to have sex with your wife sooner? Nope, he'll cry in the middle of the few times you are both not too tired to be in the mood. You're better off having him asleep in your bed and going off to the living room couch while he lets you.
It's actually nice to have the little one in bed with you. You learn a lot more about him, as well as being able to do your duties as a parent during the night, rather than leave him to his fate. Roll onto him and smother him? Just how drunk, obese or stoned do you think you'd have to be? Well... that does account for about half of N.Americans, but you might want to do something about your lifestyle rather than cast off your issue.
%$#@. It's only in the West, the same place that took the story of an empathetic man of integrity and made it into a magic-ridden, anti-sexual, justification for the authoritarianism of boy-diddling eunuchs, that anyone'd even listen to Ferber's $#!+.