Wow. Thank you. I wish I could upvote you more. I have never looked into Google's "MapReduce" but if what you say is true then my assumptions on it were completely wrong. I assumed it was 1-1 with map and reduce. But if it is generating a set of unfolds into 'essentially' fold (is it? I only skimmed the first pages due to time) then that is a very important detail and makes the name a bit of a misnomer. Why don't people make a bigger deal about this - unfold, fold is not harder but it requires a different mindset and approach than map fold.

If you are approaching it thinking it is just a map and fold then you are going in disadvantaged and will have to unlearn that fact to properly leverage something that is actually even more impressive/useful/powerful than a mare fold o map.