I guess this is the problem... GFY embeds the Youtube player as a flash application:
Code:
<embed src="https://youtube.com/v/t7tA3NNKF0Q?autoplay=0" type="application/x-shockwave-flash" width="425" height="350"></embed>
Whereas other sites embed an iframe which allows Youtube to choose the correct way to present it:
Code:
<iframe allowfullscreen="" frameborder="0" height="360" src="https://www.youtube.com/embed/m4s_mSAbk4I?enablejsapi=1&" width="640"></iframe>