"[W]e can have democracy in this country, or we can have great wealth concentrated in the hands of a few, but we can't have both."
– Justice Louis Brandeis, quoted by Chrystia Freeland, "Thanks to Pope Francis, Revolt Against the Global Super-Rich Is Underway", Huffington Post, 2014-01-21
For this and more Brandeis quotes, see http://en.wikiquote.org/wiki/Louis_Brandeis.
Ironically, just before I was reading Freeland's article I heard on an old "Godmorgon, världen" podcast that Rush Limbaugh called Pope Francis a Marxist. See "The message of Pope Francis can survive Rush and the rest", Mary C. Curtis, Washington Post, 2013-12-06.
So, according to Rush Limbaugh, Justice Louis Brandeis was a Marxist.