URL shortening is a technique where a provider makes a web page available under a very short URL in addition to the original address. There are hundreds of provider out there, but only a few of them provides public api and crossdomain.xml. I put toghether some of those that work and URLShorten class was created 
feel free to use it and enjoy
Update: jdem.cz, tinyurl.com, bit.ly, tr.im, is.gd providers implemented.
It may be not popular, but it is possible to substitute / override whole class from .swc file. Lets say you are using some public api, in our case Facebook actionscript api. I admire work of developer team, but I would like to have some things different. My facebook application requires publish_stream extended permission right after user login (authorize) my application. Even if official facebook api documentation says it is possible to ask for extended permission with login.php call (req_perms parameter), our facebook actionscript api does not offer setting this parameter.
When you keep getting:
Flex Error #1034: Type Coercion Failed: Cannot Convert *** to mx.core.IFlexDisplayObject
… after using getDefinition() method, in my case:
// url = "../some.swf"
var request:URLRequest = new URLRequest(url);
var context:LoaderContext = new LoaderContext();
context.applicationDomain = new ApplicationDomain(ApplicationDomain.currentDomain);
loader = new Loader();
loader.contentLoaderInfo.addEventListener(Event.COMPLETE, assetsComplete);
loader.load(request, context);
...
// assetsComplete()
var applicationDomain:ApplicationDomain = assetsLoader.contentLoaderInfo.applicationDomain;
var assetsClass:Class = applicationDomain.getDefinition("Assets") as Class;
...
The problem is, in fact, the security not coercion! Try move your .swf (the one that is beeing loaded) into the same directory where master .swf file is located.
Lets see how to convert between Bitmap, BitmapData and ByteArray in few examples:
