This morning's Washington Post  has a story about the increase in homelessness in Washington, D.C. - 13 percent higher than the previous year - mostly on account of the decrease in affordable housing units. D.C. real estate prices have come roaring back and gentrification is claiming more and more parts of the city. So, my question to our more libertarian-inclined friends, who dislike government intervention into the marketplace: What is to be done about this rise in homelessness? It affects mostly single moms who are already pretty vulnerable. Should the government step in? Is there a real market-based solution lurking in the shadows?