Great, now this has got me wondering, how DO they reproduce? You never see any pregnant Navi women, but there's no indication they lay eggs either. I get that those tentacles double as their genitalia, but where do the children actually come from?
Hmm, perhaps there's more to the Smurf comparison than I even thought, because I've long wondered how they reproduce (even before the Venture Bros "single female servicing a large colony of males" discussion between the henchmen)
See, Smurfette isn't even a natural Smurf, but a creation of Gargamel originally used to tempt the Smurfs into a trap. It's only after she's accepted into Smurf culture and feels guilty about her role in the potential destruction of the Smurf village that she turns her back on Gargamel...
Holy crap! Smurfette is the Avatar!
As for reproduction, long ago I decided that the Smurfs were not in fact animal life, but were a type of intelligent fungus, reproducing asexually. The first step of the Smurf life-cycle is a mushroom, which eventually grows to full size and the humanoid-shape creature grows within it. Then the fully-formed smurf hollows out the mushroom further and emerges, the shell of the mushroom is used as a house from there.
I think maybe the Na'vi have a similar life cycle, and are actually a type of intelligent seed that falls out of their huge tree. Maybe that's why they connect so easily to the trees, and the other animals with USB connectivity are just from different types of plants.