Advertising/Sponsoring. If it's free then someone else aside from Yahoo is putting money, and if that is the case then it's targeted at Americans. If they can get Australian sponsors I figure you could get/watch it for free too. At least that's what I've come up with as an answer for such things. It happens here in Canada for the TV buisness where TV shows regardless of where they are from it's required to use canadian commercials when on break.