The recent oil spill in the Gulf is an object lesson -- corporations exist in opposition to public welfare. The problem is that the corporation is like a virus; it's sole purpose is to grow and survive. Corporations cannot consider ethics, or public well-being, just CAN'T, unless this can be seen to be beneficial to growth and or profit. This is not because the corporation is blind, or callous, but because legally it exists to benefit its shareholders, and only its shareholders. Spending corporate profits to install protective devices to safeguard wetlands is a poor corporate decision, but a good decision from a human standpoint. The cost of the clean-up may change the corporate cost/benefit analysis, but probably not.
Private companies can make choices that benefit the community, or the planet, because the owners can decide to reduce profits, or slow growth, if they choose. They can operate ethically, be loyal to employees or customers, because they are controlled by the owners. This is not to say that all private companies are good, and all corporates are bad. There are corporations who feel their long term profits and growth are tied to being good citizens and stewards. And their are private companies that rival BP in their quest for profits above all else.
But companies can at least ask the right questions. The corporation can't even ask.