So this was a little handwavy, because the url styles can change at any time.  But the idea was if it's a youtube embed, your regexp has already selected for that, so now we're just selecting for the video string in the attribute of the style src="http://www.youtube.com/embed/MfstYSUscBc"

I could put it there, too -- would make the regexp slightly more efficient. My thought proces was that if YT changed the embed address (say, to embed.youtu.be, for example) that would leave us fewer places to change the string. I'm not married to either way.