With ng-bind-html-unsafe removed, how do I inject HTML?

Instead of declaring a function in your scope, as suggested by Alex, you can convert it to a simple filter :

angular.module('myApp')
    .filter('to_trusted', ['$sce', function($sce){
        return function(text) {
            return $sce.trustAsHtml(text);
        };
    }]);

Then you can use it like this :

<div ng-bind-html="preview_data.preview.embed.html | to_trusted"></div>

And here is a working example : http://jsfiddle.net/leeroy/6j4Lg/1/

You indicated that you're using Angular 1.2.0... as one of the other comments indicated, ng-bind-html-unsafe has been deprecated.

Instead, you'll want to do something like this:

<div ng-bind-html="preview_data.preview.embed.htmlSafe"></div>

In your controller, inject the $sce service, and mark the HTML as "trusted":

myApp.controller('myCtrl', ['$scope', '$sce', function($scope, $sce) {
  // ...
  $scope.preview_data.preview.embed.htmlSafe = 
     $sce.trustAsHtml(preview_data.preview.embed.html);
}

Note that you'll want to be using 1.2.0-rc3 or newer. (They fixed a bug in rc3 that prevented "watchers" from working properly on trusted HTML.)