I've never understood why it was supposed to be so earth-shaking. Even if true, there's no reason that you have to use embedding. And human beings don't really parse via stacks: we can't parse many deeply center-embedded sentences and other garden path sentences even if they're "valid" under some context-free grammar.

That CFGs model so many languages so well is fascinating and puts constraints on the language faculty, but if some language happens to not use the full power of it, that shouldn't come as quite such a surprise. Semantics are not context-free and we know that the underlying brain mechanism is far more complicated than finite-state-machine-plus-stack.

A full study of Piraha would likely be illuminating if it really is as different from other languages as Everett says -- and it's practically useless to have him say only "It doesn't have feature X". Unless he can also show that a Piraha child can't learn another language -- that would really mean something.

The fact that linguists make a controversy out of it means I must be missing something, but I can't figure out what.