don't use root as the default 'this' for a bound function, use an empty object instead.

underscore.js

@@ -366,7 +366,7 @@
   _.bind = function(func, obj) {
     var args = _.rest(arguments, 2);
     return function() {
-      return func.apply(obj || root, args.concat(_.toArray(arguments)));
+      return func.apply(obj || {}, args.concat(_.toArray(arguments)));
     };
   };