I knew a mother who was expressing for her baby in special care. By mistake, her expressed breastmilk was given to another baby, and this meant her own baby had no ebm when it came to feeding time and had to be given formula. When the mother came into the scbu she was told all this and she went ballistic - and rightly so. But it was a human error. As I recall, she made a formal complaint.
Babies in scbu can't always be with their mothers, but there is no reason for the common practice in US hospitals for healthy, term babies being separated - this is one area where we do things better in the UK! There are many reasons why babies and mothers should be together and feeding the right baby is just one of them.
Yes, I have 'done it' - fed a friend's baby in an emergency and I didn't let her know first (not possible) but she was fine about it. I would have expected her to do the same for me, if she had to.
But it is a big deal in our culture where it's hardly ever done. People have a right to feel what they feel about the exclusivity of it, and given the circumstances, women should be able to consent to it first. It is a great way women can support each other and help each other out - and on one level it's no different from giving a baby a bottle of formula, which most people wouldn't mind. I wish it was done more often, to be honest, and thought of as normal.