Are Rationality and the Efficient Markets Hypothesis Useful?

Just a quick note on the efficient markets hypothesis, rationality, and all that. I view these as important contributions not because they are accurate descriptions of the world (though they may come close in some cases), but rather because they give us an important benchmark to measure departures from an ideal world. It's somewhat like studying the effects of gravity in an idealized system with no wind, etc. -- in a vacuum -- as a first step. If people say, yes, but it's always windy here, then we can account for those effects (though if we are dropping 100 pound weighs from 10 feet accounting for wind may not matter much, but if we are dropping something light from a much higher distance then we would need to incorporate these forces). Same for the efficient markets hypothesis and rationality. If people say, if effect, but it's always windy here -- those models miss important behavioral effects, e.g., -- then the models need to be amended appropriately (though, like dropping heavy weights short distances in the wind, some markets may act close enough to idealized conditions to allow these models to be used). We have not done enough to amend models to account for departures from the ideal, but that doesn't mean the ideal models aren't useful benchmarks.

Anyway, just a quick thought...