Lots of things are "down the stack". The servers, the building they sit in, the electricity that runs the building, and the coal/water/solar/wind that produces

Lots of things are "down the stack". The servers, the building they sit in, the electricity that runs the building, and the coal/water/solar/wind that produces that electricity. Should Twitter run a power plant? Maybe they should optimize the design of current power plants? Also, what about the toilets that their programmers use - they could probably be optimized as well!