I remember reading this several years ago. It's not something that is 100% implemented by configuring emacs or vi properly: read the entire article slowly.

I'm surprised I haven't heard any Python coders piping up. We pick spaces or tabs, and stick with it; otherwise, our code doesn't run. Mixing tabs and spaces is pure evil.

I prefer spaces, because a space is a space and will display as exactly one space in any text editor.