The assumption is that the universe is a closed system therefore decreased entropy in one area requires an increase somewhere else, and as work can't be produced perfectly you'll end up in a state of maximum entropy (eventually).
So the analogy is we can expect a few sand castles to appear in the universe somewhere? I really didn't like his explanation or assumption on this. At the big bang the universe was in a state of high entropy - it was uniform. So how can it go lower?