[pron]

For the exact same reason they chose Go now, and the reason they'll switch to something else (much better!) in two-three years: because that's the current fashion.

Nothing says "I'm keeping up with my professional development" than relearning IO libraries and build tools, and rewriting in-house code, over and over again, every time in the new langue-du-jour.

[zappo2938]

Meanwhile Facebook is enjoying working with a large PHP code base. When asked they say they can write code that takes time to compile that runs fast in C++ or write code fast in PHP that runs slower. Writing features faster gives them they edge. They have an engineering team that does nothing but optimize PHP. For them an optimization is an acre of servers saved. They if something needs to run blazing fast can write code in assembly language.

What I'm told about Node is the JavaScript is running in a single thread but all I/O is being passed to native code which is written in C++ and running on multiple threads. It does use all the CPUs.