If threads or processes or distributed computing is being used under the covers, does it still count as multi-threaded programming? I could go out and design an machine/OS that didn't use what we would think of threads (think Atari's Transputer [1]), and all these implicit threaded schemes would still work with my new construct. Now, we might not have transputers, but some of us get to use GPUs and such (still niche, but growing), where the unit of parallelism no longer resembles a thread very much.

My point was that multi-threaded programming hasn't taken off because it hasn't needed to. We just get some really smart experienced guys to write our infrastructure that encapsulates thread use and all of us get to reuse that.

[1] http://en.wikipedia.org/wiki/Transputer