If your URL turns into a hyperlink when typing it in the post, you must remove the link from it in order for it to work. In other words, if it looks like http://www.youtube.com it won't work, but if it looks like http ://www.youtube.com it will. You can unlink it by clicking the "broken chain link" button to the left of the anchor button (if using the enhanced editor).
Trying to embed multiple movies into a single post is not reliable. It's best to add additional movies into replies to the original posting.
Please keep embedded movies relevant to the topic of each subforum. "General" movies should only be placed in the Nether Region.
Links to obviously copyrighted materials will be moved. (It's a liability thing)