The rumour i heard was that a cobra will only strike a static (non-moving) object, and when you watch charmers, what they do is move their hand or flute left and right so the cobra is ready to strike (hence the pose) but doesnt because the charmer never stops moving. You'll see them constantly moving left to right all the way up until they slowly put the basket lid back down on the cobra.
Also seen in doco's with cobras, the host (Austin stevens, Irwin ect) will make the snake fixate on one hand then move it constantly left and right and while the snake has its attention on the moving hand they usually use the other hand to touch them on the back of the head.
In the Austin stevens vid recently, you can plainly see that the snake was watching his right hand, and for that split second that stevens stopped moving it, bang, he was bitten.
Cheers, Alan.