[silin]

стало интересно: а вдруг ?
эксперимент:
пишем, ошибок не дает..

package {
	import flash.display.MovieClip;
	import flash.net.*;
	import flash.util.*;
	public class mc1 extends MovieClip {
		public function mc1() {
			var so:SharedObject = SharedObject.getLocal("tmp","/");
			so.data.mc = new MovieClip();
			so.data.mc.graphics.beginFill(0);
			so.data.mc.graphics.drawCircle(50,50,50);
			addChild(so.data.mc);
			so.data.num=new Number(7);
			so.flush();
		}
	}
}

читаем..

package {
	import flash.display.MovieClip;
	import flash.net.*;
	import flash.util.*;
	public class mc2 extends MovieClip {
		public function mc2() {
			var so:SharedObject = SharedObject.getLocal("tmp","/");
			for(var prop in so.data)trace(so.data[prop]);//7 undefined
    		addChild(so.data.mc);//Parameter 'child' must be non-null.
		}
	}
}

выходит, что низя..
liveDocs:" Each attribute (of ShsredObject.data) can be an object of any basic ActionScript or JavaScript type—Array, Number, Boolean, and so on."