My Pro Site blog owners have been having problems embedding videos and A-Stores, etc. To test the problem I first went to one site and embedded regular YouTube embed code in the HTML tab. Like this:
<iframe src="http://www.youtube.com/embed/FQlZ3ORRV2I" frameborder="0" width="399" height="203"></iframe>
It worked fine. I told the user step by step how do to it, but she still had problems. (Code disappearing or not being visible.)
Today, I added myself as an admin to her site (as opposed to working on it as the super admin). I went to the same test post and simply resaved (updated) the page, with no changes. When I did so, all the embed code (like that above) changed to shortcode, like this:
This latter code, btw, does not retain the sizing info, etc.
So now I suspect the problems are resulting from some strange setting that is keeping them from adding code the way the super admin does and from the way a NORMAL WordPress install does.
Fortunately, I can still edit this post (would be nice if replying to posts were allowed before a staff member replies). I found the problem. Unfortunately, no one (including admins) on a multisite are allowed to embed code. They can only (as far as I can tell) use oEmbed, which limits what services they can use and the features they can access. Blah.