If you try to embed a YouTube or other video using Safari in the Blackboard content editor (found in blogs, wikis, content items, etc.), you may get a blank box when you submit. Blackboard has verified that this is a bug (KB article 000041436). The iTeam will update this post when the bug has been fixed.
In the meantime, to embed video content, you are encouraged to log in to Blackboard using a current version of Firefox from a Mac or PC.