I tried to use shortcode from youtube as mentioned here:
If I use a youtube url, for example:
it works great in postings, showing the embed without having to use the embed code of youtube.
But when I do the same in a widget in the sidebar (in a text box) it shows the url but does not use/pick up the embed code.
Perhaps this is the same problem why tubepress, smartyoutube shortcodes do not work in boxes.