I see the "bubble" issue differently. Everyone has context bubbles already. You have work, outside of work, your hobbies both online(IE HN) and offline. You in

I see the "bubble" issue differently. Everyone has context bubbles already. You have work, outside of work, your hobbies both online(IE HN) and offline. You influence these bubbles composition. Hobbies in particular are entirely self selected. But you are aware of which context you are communing in and are free to move between them and outside them into the general public sphere. I see this as more of the same. As you say, "its at least transparent, people are aware of it or have to opt in" Interestingly by the comments here, a big driver for these self selected bubbles are so that people can avoid the advertising they don't wish to see. IE Pinterest and other SEO spam. If "self selected bubbles" are bad, then "targeted relevant advertising" is worse.