Here, Gene discusses the fact that we really don't have ideal types of spontaneous and planned orders. It's a great post - please click through and read.
I think this is exactly right, and I think a fair amount of people recognize this, particularly people who get into governance questions. Jerry O'Driscoll confirms the point in the comment section.
The trouble, I find, is that precisely because these things are so fluid, whether you appreciate "spontaneous order" or whether you are guilty of planning often has more to do with the person you're talking to than any solid analytic point. This is frustrating, but it's a common problem.
The other point is that "planning" can emerge spontaneously precisely because planning can be functional. Planning behavior emerged naturally in biological evolution. Why would you expect any different in social evolution? This is the Coase/Williamson point, and it's also one of the few things that Hoppe doesn't do that bad of a job pointing out.
As we see with the American Constitution, planning can also consciously leverage spontaneous orders.
So it's important to remember that these lines are always fuzzy, and "spontaneous order" and "planning" are more tools for thinking about these problems than they are ideal-types. Remember that, and don't count on everyone who blathers about "spontaneous order" and "central planning" to always understand that themselves.