Why Is Controlled Crying Controversial?

For a description of what CC is, see here.
And how it's done, see here.

In some parenting circles controlled crying (or "Ferberising", as Americans someitmes call it) is very frowned upon.  It prompted Dustin Hoffman, in the movie Meet the Faulkers, to ad-lib the line "We didn't Ferberise our children, we Faulkerised them".

Proponents would say that everybody benefits from a good nights' sleep, that both babies/children parents will be at their best for having a reliable routine and plenty of rest.

Critics say that it's unnatural to sleep apart from our babies/young children, or to expect them to go periods up to 12 hours without so much as a drink of water.  That they are too young to understand anything except "Mummy doesn't want me", and that there are kinder ways to get children to sleep through the night.