add a defaultText option to knockout-sortable (https://github.com/rniemeyer/knockout-sortable). the defaultText must be contained in a span.injected element or else it will not be removed properly. thanks to @mbest for the help, and a related stackoverflow question can be found here: http://stackoverflow.com/questions/20407640/knockout-js-knocko…

knockout-sortable.default-text.js

var origForeachUpdate = ko.bindingHandlers.sortable.update;
ko.bindingHandlers.sortable.update = function(element, valueAccessor, allBindingsAccessor, data, context) {

	var options = valueAccessor();

	if (options.defaultText) {

		var hasDefaultText = $(element).find('span.injected').length > 0;

		var array = ko.unwrap(options.data);

		if (!array || !array.length) {
			element.innerHTML = options.defaultText;
		} else if(hasDefaultText){
			$(element).find('span.injected').remove();
		}
	}
	origForeachUpdate.apply(this, arguments);
};