The recent news that the nation's 400 biggest charities have seen donations dropped by 11 percent last year (the worst decline in 20 years) is proof that governments must intervene in the market to take care of basic human needs.
While charities are an incredibly important part of our society and culture, the good will of the better off cannot be counted on in times of need, and the government must have an infrastructure capable of serving those who cannot fend for themselves. Libertarians often cite the 'efficiency' of charities, claiming they are often better at alleviating poverty and providing education and assistance to the poor. While they may be right (I have yet to see a persuasive study though), if charities don't have any money, it is an irrelevant point.
When charity money dries up in America, there is nowhere else to go. While Europeans can rely on the government to provide health care, welfare and housing, Americans must literally go out into the streets.
If that isn't cause for a socialist revolution, I'm not sure what is.