After MongoDB published their write speed benchmarks based entirely on unacknowledged writes (e.g. how fast can you write to a socket?), it's been a long downhill ride with an immense amount of inexplicable ignorant support.
From my own memory, I don't recall 10gen ever posting misleading benchmarks. There were a bunch of other people who did so, and 10gen did little or nothing to try to shut that publicity down.
That said, I think that the 'how fast can you write to a socket?' default setting was probably intentionally put in place to make benchmarks look good.
