http://www.youtube.com/watch?v=0aRIlnQzw-A&feature=player_embedded
YouTube not only gets 2 billion video views per day as one of the biggest video sites in the world, but now it has announced that it crossed the 1 billion subscription mark. In other words, YouTube is now sending more than 1 billion notification e-mails every week. The yellow subscribe button made its debut in 2006.
YouTube subscriptions allow users to follow users and/or channels so that they can always stay updated on new videos from them. 15 channels have more than one million subscribers: fred, nigahiga, kassemg, shanedawsonTV, shanedawsonTV2, smosh, universalmusicgroup, machinima, sxephil, mysteryguitarman, davedays, kevjumba, realannoyingorange, raywilliamjohnson, collegehumor and failblog.
To commemorate the milestone, YouTube has announced a new subscription widget that video makers can embed in their website. This widget allows users to subscribe to YouTube videos without having to visit the YouTube website. The embed code is an iframe and needs to be pasted into the source code of HTML code, in the same way you would embed a YouTube video.