Canadian charities used to ship literally tons of dried cow's milk to developing countries, only to learn that they were solving an immediate problem at the cost, not only of causing long-term damage to local economies (as described at Iains' link), but also of exposing those who drank it to the threat of contamination in the water used to reconstitute it.

In some countries -- Japan and much of China, for example -- milk is not part of the regular diet; even children don't drink milk after they are weaned.