When a person hits that subscribe button they are saying, I want this person's content... not I want you @Youtube to decide what portion of content I get.... C'mon guys, to subscribe is an action, which means that sub is saying, give me this content
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That's what the bell is. It's an opt in per channel for notifications. Not everyone wants push notifications on the phone/email for every sub they have. So youtube added the bell. If you want notifications for *that* channel, push it.pic.twitter.com/ui8AkKjaTJ