It doesn't currently seem as though there is a way to do live events in YUI similar to jQuery: http://api.jquery.com/live/

It sure would be nice if something like:

function handleClick(e) {
    // click!
}

YUI().use('node-base', function(Y) {
    Y.on("click", handleClick, ".foo");
});

caused handleClick to be fired when a node with the "foo" class was clicked on after being dynamically added to the DOM and sometime after the Y.on was evaluated. I feel like live events are one of jQuery's killer features that YUI lacks.