I don't know if it's a problem in your application, but you can always load your service URL's from a XML config file at runtime. I think this way they won't be visible after decompilation of your swf.
But if someone wants to look where your request are sent, it's not a problem. He will just use web debugger like Fiddler and see the outcoming request URL's. But config XML file is a good idea, because your development services are usually on different severs than your production environment. This way you can change your service destinations without recompiling swf.