Why doesn't youtube embedded source show up in the WYSIWYG?

<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/fSDUklJqj30&hl=en&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/fSDUklJqj30&hl=en&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>