And did you know there is a facebook group for sharing breastmilk? Eats on Feets is a global network of women who share breastmilk, and there are facebook groups for it everywhere, including one for the NT.
I found out about this because the US Food and Drug Administration has recently issued a warning to mothers about sharing breastmilk this way, warning of the potential risks of chemicals, diseases etc in milk unless it is screened. The FDA's press release has been widely publicised by Thomson Reuters, whose declared interests include Abbott Laboratories, Watson Pharmaceuticals, and Nestle SA - but if you read right through the article it's pretty fair. However, the FDA's original press release is here and is a more practical guide as to how to use or donate human breastmilk in the US.
But it's not rocket science - essentially if you want to use another woman's breastmilk, you want to be satisfied that they have taken the same precautions you would take if you were breastfeeding your own baby. They shouldn't consume drugs which would get into the milk, they should use sterilised bottles and mark the date of expressing etc. You need to be careful they don't have HIV or other diseases which could then infect your baby. So, you need to trust your donor and they need to agree to be screened for diseases.
In other words, you can make an informed choice to share breastmilk - it's not necessarily dangerous. I suppose the point being made is don't just assume shared breastmilk from anyone will be better without doing your homework.
For an in-depth look at the law and ethics surrounding contemporary breastmilk sharing, there is a book by Alison Bartlett and Rhonda Shaw called Giving Breastmilk: Body Ethics and Contemporary Breastfeeding Practice. There is also a fascinating article by Virginia Thorley about the history of sharing breastmilk in Australia from 1900 to 2000. It seems we have always done it, but formal advertising for 'wetnurses' has declined over the century, being replaced now by more informal feeding of the baby by family and friends, sometimes known as 'cross-nursing'.