Why do Nannies and parents jump the second their baby cries? Do you not realize that you're setting yourself up for doom? Let the thing cry. The baby is fine...they cry for no reason whatsoever sometimes.
And also, to the people who stare at the Nannies and parents who actually do let their baby cry: Mind your business. If a baby is crying in a stroller, chances are it doesn't want to be in the stroller. But why take the child out and teach it a bad lesson?