[DawnsMinstrel]

Yep, that's right. The default for uploaded videos is for them to be publicly viewable since, if you think about it, that's really the main idea behind YouTube. It provides ordinary people a chance to "broadcast" themselves. It is possible to make a video private in which case you specify which of your "friends" are allowed to view it.

Once a channel owner uploads a video to his/her channel and makes it public, anyone can link to it which is why Jesse Joe and others have been able to embed videos here in this forum.

One thing: if you're a channel owner and you have subscribers, subscribers are alerted to new videos uploaded to that channel via emails and notices that they get when they log in to YouTube. But I don't think subscribers would get a notice just because a playlist has had something added to it. That's one weakness of the approach I suggested above. The channel owner would have to have a way of letting interested people know that new videos have been added to playlists.

There is a way to do this on YouTube but you'd have to use the "friends" function rather than just the subscriber function. What you would do is ask all subscribers to be friends. Then when you add new videos to playlists you can send out a "bulletin" from your channel to all your friends announcing the additions.