I have not read Strauss, although I have read about him in articles like Orwin's for several years. Maybe it's finally time to crack a book. In fact, I am becoming so intrigued by him that I may even attempt a disciplined approach to his work and look for guidance in how best to read him.
It's not quite as simple as Orwin puts it. The great example of the need for esoteric writing is always the trial and execution of Socrates -- in democratic Athens. So it's not just the rulers philosophers have to watch out for. But it's still a means of saving the philosopher from people who might wish to do him harm, not a way of exercising power.