If you have a Live Space and want to add video from Youtube, or Soapbox to them you currently seem to have two options.
1. Adding the Embedded Video gadget
Flollow this link (http://gallery.live.com/liveitemdetail.aspx?li=2315d37d-74af-469a-84c5-3eb1da763325&l=1) and add the gadget to your space.
You can easily select a video on Soapbox, Youtube etc.. copy the HTML code and paste in the gadget. It's like adding pictures to the picture gallery on your space. The biggest difference is that the video gadget can only point to 1 video currently so you will need to add one gadget per video you want to display. Still nice to display a video of the week for instance.
2. Embedding videos in your blogposts on Live Spaces
A guy named Scott (http://scottisafooldev.spaces.live.com/) write a video plugin for Live Writer (http://windowslivewriter.spaces.live.com/). This one will check whether your blogging engine (Live Spaces, Community Server, WordPress) allows the embedding of video. In case it doesn't (like Live Spaces currently doesn't allow the embed tag in blog posts) only an image is added with the first screen of the video and then this image links to Youtube or Soapbox or... Kind of cheating but better than nothing.