I would use milk from a friend but I don't think I'd use it from a stranger. I might if I was desperate though i.e. if I had a newborn because I would definitely not ever give a newborn formula. DH agrees with me too and if something ever happened to me he would make sure our baby got breast milk if he could.

The breastfeeding mother you get it from is obviously feeding her own baby too. So I think it's a pretty low chance of anything being 'wrong' with the milk if they're giving it to their own child iykwim.