It seems like I've seen a few questions about the autoplay feature not working for Youtube videos embedded in campaigns. I thought I would post a short guide on how to get this to work. This workaround is valid as of 3/4/2014.
It should be noted before starting that this appears to be a Youtube issue, not an OP or Reforge issue.
1) Pull up the video you wish to embed in Youtube, and click on the "Share" button near the description.
2) Do NOT use the abbreviated URL under "Share this video". Do NOT use the first URL or any of the code provided under "Embed" (with "/embed/" in URL).
3) DO use the URL provided in the code after you select the check box for "Use old embed code". This should have a "/v/" in the URL.
4) In the page editing screen on Obsidian Portal, click "Media Embed" on the right hand side of the editing field. You will be prompted to enter the URL - use the one from step 3.
5) In the URL, change "version=3" to "version=2&autoplay=1".
6) Save and the video should autoplay when the page is loaded.
Code that WILL autoplay: