I am using FCK editor, and allowing object tags to be entered... however, the only way to do this seems to be for the users to enter the tags in the SOURCE section... most users aren't so hot at techy stuff like that...
You're right: users entering tags is pretty much a recipe for trouble.
I would suggest using specific plugins for the content you want to allow users to add.
I'm more familiar with TinyMCE, but I'm sure there are a wide array of FCKEditor plugins for stuff like YouTube. For instance Youtube plugin for FCKeditor.
Add it to the allowable tags in fckconfig.js as such:
FCKConfig.ProtectedSource.Add( //gi ) ;
If you want to allow video, you better provide a plugin so that user can do it easily and not go to source view. Source view is a last resort, pretend it does not exist or even disable it.
It is quite easy to do actually. I did something like that at my forums: How to insert a video. Here's the code of the plugin: fck_postvideo.html and fckplugin.js.