Pharyngula has a good post discussing how baby formula manufacturers are thwarting pro-breast feeding advertising campaigns in the US. I'd never much thought about baby formula or breast feeding until I took a class with Tobias Hecht, an anthropologist (and exquisite educator) who spent a number of years working with the street children of Brazil. He details his experiences in the book, "At Home in the Street: Street Children of Northeast Brazil," which I highly recommend (note: I haven't read the full edition of the book; I've only read excerpts of drafts).
One of the topics of Dr. Hecht's class was the politics surrounding baby formula in impoverished areas. Formula companies (most notably Nestle, as I recall) in these poor areas of Brazil would provide new mothers with a week or two of free baby formula (something US companies apparently still do, according to Pharyngula's post). The mothers, wanting to take advantage of this wonderful gift of western technology and medicine, fed their babies exclusively using this formula for a week or two. In that time the mother's milk would dry up, and thus when she ran out of formula she couldn't switch back to breast feeding. Since most people in the area were too poor to afford enough formula, they would instead either dilute down what little baby formula they could afford, or feed their babies rehydrated powdered skim milk or other medically disastrous foods.
There are definitely legitimate uses for baby formula. However, when formula companies actively seek out profits by giving new mothers just enough formula for their milk production to dry up, they're crossing the line into what should be criminal activity.
I introduce this history to students in some of my classes, and a common response is, "But the makers of baby formula add everything a baby needs to the formula, so it's probably even healthier than breast milk, right?" Unfortunately this is false, and the reasoning is simple. While we can identify the major components of the foods we eat (amount of protein, fat, vitamin C, etc.), we simply can't identify all the less abundant molecules that are present in our food, be it mother's milk or broccoli. We can't even identify all the specific proteins in the food item in question.
Since we don't know exactly what's in our food, it is impossible to test which specific molecules are important for growth and development, and thus it is impossible to know if we are adding everything we need for ideal growth and development to baby formula. Additionally, even when we identify important molecules, it can be nearly impossible to synthesize or duplicate biologically created molecules (e.g. antibodies, specific proteins) found in natural foods like milk. Certainly baby formula has been tested at an overall level, and children who are reared on formula appear to perform about as well as children who were reared on breast milk, but this still doesn't mean that baby formula contains everything it ideally should.
As an example, take something like a strawberry: there are more than 350 different chemicals in a single fruit that combine to give us the classic strawberry taste. There are probably countless thousands, if not tens of thousands, more unique molecules in an individual strawberry that we can't taste, and I'd wager that most of them have never been identified.