For those of you who don't know the term, Social Darwinism is the philosophy of applying Natural Selection and Evolutionary "Survival of the Fittest" ideas to that of modern Human Society. It is a common argument against welfare and universal healthcare. If thought of in full perspective would also be the opposition to affirmative action, sex inequality in the workplace, and the like.
I personally believe that in an ideological sense, the perfect case, that it is a fair and just philosophy. Evolution, whether biological or social, is the quickest, straightest, and most well rounded path to advancement. With the diseased dying, the poor not leeching the resources, or the stupid being kept alive by restrictions (i.e. no laws requiring wearing seat belts, etc.) that our global society would economically prosper ad the human race would biologically evolve with the loss of debilitating genetic diseases.
I do, however, realize that in a practical and realistic sense that this is not a good policy to hold. When factoring in morals, ethics, and the way modern society has already developed, social Darwinism would work about as well as anarchism, and those who should prosper from it (The healthy, economically sound, and intelligent citizen) would likely suffer through riots, and become the target of those who realize their death is near because they are not the fittest.
There is one instance where I do believe in the practical application of Social Darwinism and that is in free market capitalism. If you cannot sell your product, manage your finances, or hire whomever can do the needed task the best, then you have no place in running a business. (I.e. A.I.G. should have been let to fail).