It sadden me that they make Jeff Dean work on these kind of issues. His map/reduce invention brought to the world a lot more than managing his coworker egos.
If managing people were the same skill set as computer science perhaps we would not be seeing this play out as it has.
This is seriously a massive failure on the part of Google to handle their own shit. I often wonder if these people are too old or out of touch to appreciate how this kind of thing may or may not blow up on social media.
To not consider how this might cause public relations issues especially when dealing with someone who has an established social media presence seems like a misstep.
On the flip side maybe they thought it was worth it. Weather the storm for a few days and twitter will move one. It's hard to say.
The mappers, shufflers, and reducers are all independent of each other, reading and writing from the filesystem, and managed by a coordinator. There's nothing like MPI, other than the use of the Stubby RPC system, which sort of resembles MPI but has completely different distributed communication semantics.
The correct name is really MapShuffleReduce and the most important step is the shuffle, because it's a distributed sort. Of course, they didn't invent distributed sort, but combining these three concepts together in a distributed fashion and running it as a production system is really what was important.