Yup - Merlin Mann - his HipsterPDA blog post it still up online (I linked to it on my own blog post). I've been using index cards that way for decades thanks to him. I did progress and upgrade to Notsu dot grid cards.

There are a lot of 'productivity' systems now that use the 3x5 index card format, Ugmonk and others. All just capitalizing on cool, well made gear vs. using the damn things. But to each their own. I'm minimalist and a cheap-ass, I also have spent my lifetime hacking things to make them better for my own needs.