I thought it would be interesting to create a comparable example of this mini-app with basic YUI 3 code: http://jsfiddle.net/ericf/wpuCm/
backbone.js seems like a great library, and MVC is on the YUI 3 roadmap ( http://yuilibrary.com/projects/yui3/roadmap ), hopefully some of the concepts from backbone get implemented in the YUI’s MVC layer.