Problem: When editing a page with an embedded YouTube video, you don't really get a good feel of what the page will look like when you save it.
http://cl.ly/image/1X1B0o1Z0B2R

Solution:
We should be able to modify the widget connector code to make use of the Confluence 4 rendererd placeholder API: https://developer.atlassian.com/display/CONFDEV/Providing+an+image+as+a+macro+placeholder+in+the+editor

YouTube provides a dead simple way to get the image of your video:
http://stackoverflow.com/questions/2068344/how-to-get-thumbnail-of-youtube-video-link-using-youtube-api

So when you are editing the page you should now get a rendered placeholder with an image of what it should look like!