I make my views known as well as do my best to share information about milk sharing, formula and breastfeeding in general with every mom I can! And in these conversations, I often hear a lot of reasons why mothers can't or won't breastfeed and choose to use formula. When informed about donated or shared milk I hear women express fears about everything from Chemical Exposures to HIV to low nutrition. I tend to feel these fears are due to the fact that most parents - and doctors - do not have the the proper education to truly make informed choices.
The article below provides a good basis of comparison between formula and shared breast milk. It provides both pros and cons for using both formula and milk. Even if you aren't questioning whether or not to use formula or donated/shared milk it's good information to have!