Chatty software able to synchronize state over the open internet using declarative concurrency is a distributed system. A high performance cluster running something like distributed message passing concurrency erlang is a distributed system. A single program written with the complexity of shared state concurrency executing over multiple cores is a distributed system. The concept of concurrency is vital for this, particularly what type of concurrency used. When this person talks about distribution what kind of concurrency is he referring to? I'd like to see this professor reimplement Dropbox for sequential execution on a single CPU to serve the world (you can only use shared state, or any other form of concurrency if you do it on the same CPU). This centralized system then should be fault tolerant. Which it absolutely will not be, as you need at least two machines for fault tolerance. This article was a waste of time.