Theoretically you can do that. On the demo site it is being removed, because we don't allow users other than administrators to submit potentially disruptive code such as iframes (script tags etc) in content elements.
I just tested on my localhost and here is the result:
easycaptures.com/fs/uploaded/549/4053404521.jpg
It works with compojoom.com in iframe, but for some reason it didn't work with google.com. (just mentioning this - so it seems that the kind of website you want to put there matters)
Regards,
Daniel