Regardless, I take exception to the claim that they "often don't predict the real markets all that well". They can predict real markets very well in most scenarios. Most theoretical-basis predictions of price ceilings and floors (such as rent control or minimum wages) are perfectly sound, but there is plenty of ambiguity in the results that critics seem to misinterpret as proof of the failure of Supply and Demand to predict outcomes.
Price ceilings tend to result in shortages, but occasionally result in no effect at all. But that isn't enough evidence to say that Supply and Demand doesn't apply to this scenario. In order to disprove the applicability of Supply and Demand, you would have to show that a price ceiling increased the quantity supplied. Such scenarios are as rare as black swans.
