Good point. Here is why I don't see that as a problem.
1. Things are democratic overall. You tend to follow people that share things that you like. You see what they post AND what they "upvote". Whenever someone votes on something, it also shares to their followers. Combined with some weighting on how popular a post is, and how recently it has been touched by someone else, this effectively means that you get a list of posts relevant to your interests, sorted by popularity. Any one person leaving would have negligible impact on your feed's content.
1. Things are democratic overall. You tend to follow people that share things that you like. You see what they post AND what they "upvote". Whenever someone votes on something, it also shares to their followers. Combined with some weighting on how popular a post is, and how recently it has been touched by someone else, this effectively means that you get a list of posts relevant to your interests, sorted by popularity. Any one person leaving would have negligible impact on your feed's content.
2. You also follow topic tags.