I suspect the answer is that there is no "the" positive feedback circuit as not only can things get messed up in many ways interactions between components can make the issue that none involved intended. A simpler comical example is medical marijuana in California.

* Federal legislature dogmatically denies a medical usage. * State approves it for medicinal use. * Federal regulators threatens to arrest any doctor perscribing it. * Intended medical gatekeeping loses power

Neither party wanted that laxer level of enforcement (regardless of outcome) but together they did so.