The idea is not as crazy as it sounds. Javascript is a fairly decent language with many functional programming features (it's the html DOM that is messy and inconsistent across browsers). Additionally, languages like Ruby are known for their slowness (though they can make up for it in macro-optimization at the design level) so server-side javascript may be performance competitive. Especially so if the advances in open source JS compilers like V8 and tracemonkey make their way server-side.
I wrote a little libevent-based webserver (bush-league stuff) that embeds V8 to do its request handling over a weekend not too long ago. You could start doing this today with very little effort.