You might say by the same argument that single-line lambda expressions take care of 90 or 99% of cases, and you should revert to using named functions for the rest.

I don't think either is true -- if you have more flexibility in the syntax, you'll do more with it.

The reason for all the discussion over the years is that a single line lambda doesn't cover 90% of the cases. If you think in terms of callbacks, I bet one liner cover less than 10% of the cases.

Python already has a solution for callbacks:

    @reg_callback(button.onclick)
    def callback():
        do_stuff()

Whilst this is more pythonic I personally prefer Javascripts use of lambdas as more than a means of expression. More like a way of life for the language :-) And that is IMHO what makes it functionally closer to Scheme. Just looking at the way one defines lambdas in Javascript and their use throughout the language is a thing of beauty.