There is nothing in the server side code that removes anything from your content so most likely if something is being removed its done by the editor.
If you use FCKeditor and you add the object using Source View (Not the Flash Toolbar thing), then save without changing back from source view it should work. I suspect when you change it back to wysiwyg view from source view, it does some cleanup, by saving without switching back you can avoid this.
Note that objects are not allowed in some features like Forums or Blog Comments, but it should work fine in Html module.
Hope it helps,