Via the Canadian Broadcasting Corporation, a lively debate on the radio program Q: Q's Great Spaces Debate. You can listen to the 17-minute discussion between Farhad Manjoo and engineer-blogger Tom Lee.
Then in 1995 I read The Mac is Not a Typewriter, which made a forceful case for one space. I henceforth taught my students to use just one space, and met resistance just about every semester. Now I'm safely retired, but the debate continues.