[mjn]

I believe Friedman supported it sort of half-heartedly, because he thought the population wouldn't stand for not having a social safety net at all, and if there was to be one, the negative income tax was less distorting and less bureaucratic than the usual mixture of rent control, food stamps, and unemployment benefits.

Hayek did support it on more philosophical grounds, because he thought it would increase individual freedom. Almost the exact opposite reasoning as some libertarians, actually. It's common for libertarians to argue that social programs should be handled by private charity, but Hayek worried that doing so leads to collectivism, because people feel bound to social cliques that provide social safety for their members (ethnic groups, churches, etc.), and fear leaving the groups lest they lose their insurance. So he would prefer there be a society-wide safety net not tied to these cliques.

I kept forgetting where he had written that, so I excerpted a quote in my mini-scrapbook here: http://www.kmjn.org/snippets/hayek79_minimumincome.html