I'm a psychologist in training, and find it terrifying and shocking that so many people consider crying it out an acceptable and even "good" method. I've read the posts here and most of them state that moms are "firm believers" in this method. Well, those beliefs are incorrect, not based on reality, and self-serving. Here is the research from Harvard which shows that cry-it-out, leaving baby alone and not responding to their needs is VERY HARMFUL to babies in the long run.
http://www.hno.harvard.edu/gazette/1998/04.09/ChildrenNee...
Babies may not remember it as they grow older, but it leaves psychological marks of anxiety, fear, and later may create serious issues of trust and intimacy, and even phobias. In different cultures (India, for e.g.) babies are the mother until 3 years of age, they sleep together, spend time together, and they have much better psychological health as they grow.
The cry-it-out method is nothing but a mental invention which has little to do with baby needs, and parents responsibilities.
There is absolutely no rule as to WHEN a baby should start sleeping through the night. They do not wake up to feed only, it can be pain, discomfort, need for reassurance. So to suggest that they should be left alone to comfort themselves, because it is easier for the parent is simply CHILD ABUSE.
All the ideas that baby somehow "manipulates" or is "OK" if fed and clothed are questionable. First of all, baby does not have the psychological complexity to "manipulate" -- all it has is a mechanism to call attention to his or her needs! When you are in pain and discomfort, would you like to be left alone without help? Add to that the helplessnesses and lack of psychological strength to support oneself... Also, feeding and changing are only the physical needs of the baby, what about the need for love, touch, comfort, security? To suggest that the fed and changed baby is OK, is simply to treat baby like a machine, and ignore his or her emotional needs.
Babies are in the process of maturing and it is absolutely normal for them to wake up at different times for a few years before they reach more strength. Also the argument that this is an important "skill" to teach them (i.e. going to sleep by themselves) is another myth. Do you know ANY grown up people who do not know how to go to sleep by themselves, or eat or do other things? ALL people learn these skills without any problems, so there is no need to torture small baby with some mentally invented methods and cruel routines to achieve that.
The scheduling is also a big myth. Kids body gives signals when is hungry or in discomfort, and should be respected and followed, not to impose some artificial schedules of feeding on them. Finally, when one decides to become a parent, he or she takes the responsibility for caring for and loving the baby, so the challenges which come with it (lack of sleep, tiredness, having to put baby's needs first) are all a part of parenthood. Parents need support too, but it should not be at the expense of the small, vulnerable, and powerless to defend him or herself baby.