My intention with the CPU speed comment was to illustrate that we can't just throw more on single cores. Even distributing work across cores comes at a latency and efficiency penalty. And furthermore, even that isn't enough for some of the web scale applications that have to be spread across thousands of computers distributed across the world in order to handle the load and remain at reasonable latency.

So my point was mostly that distributed applications are unavoidable because you just can't scale up past a certain point.