Only the parent element is handling events. In this case it's the editor container element. If you add dynamicaly elements into the container you don't have to bind any events on it.
<script type="text/javascript">
$(document).ready( function() {
$('#editor').dragResize({grid:20});
});
</script>
<div class="block snap-to-grid" style='width: 300px; height: 200px; top: 200px; left: 50px;'>
<div class="block" style='width: 200px; height: 120px; top: 100px; left: 40px;'>
<div class="block snap-to-grid" style='width: 300px; height: 200px; top: 60px; left: 400px;'>
<div class="block" style='width: 100px; height: 100px; top: 200px; left: 600px;'>