Why would Jeremy talk about live-binding when Backbone does not support it?
I've talked with Yehuda long ago about data-binding and I am familiar with how it's done in Knockout.js.
We've got it working pretty awesome and have supported blocks. It's much more powerful and I feel straightforward than Knockout's templates. You simply write JS and any JS works (as long as you understand a little about closures).
It's also lighter-weight than Knockout (although it depends on jQuery, Zepto, Mootools, or shortly Dojo or YUI).
The plan is to release a stripped down Model, View, Controller, and route less than 8k, with live templating running from the above libraries.
It's currently 8.5k. It will have a new name. Look for it at JSConf.