Discoverability is a major problem with that setup then. Half of the fun of reddit has always been learning of new places and new subreddits, and if you're only watching what you follow, you can't do that. Mostly, I'm just amused by the hubriski (if that's not a word, I'm making it one) of thinking that you've solved Eternal September. If you don't know me from reddit, I was a mod of subredditdrama for a long time. I love to watch chaos, and it always comes. It comes fastest to the places arrogant enough to think they're immune to it.
Yeah, discoverability does affect Hubski quite a lot. However once you have your echo chamber built, it's lovely! I don't think eternal september won't come. However, I believe that I have the tools to sufficiently ignore it. I think a big influx of users on Hubski would play out similarly to a disaster movie: everything may be horrible, but as long as we have each other, we'll all be ok! :) On a more serious note: eternal september is how the world works. I have no problem with that, and I totally accept that on the whole it cannot be avoided. Everything that involves groups of people is in constant flux. However, despite eternal september surrounding us, permeating every facet of human life (constant change) we carve out stability. We don't descend into chaos. We take the control that we have over our life and we leverage that to get what we want. Hubski is the realization of that individual control in the context of online discussion. Also, hubski isn't some answer to Reddit. It's different, but not "better". Just like Twitter and Facebook are different from Reddit. I just want to talk to interesting people and have conversations I'll enjoy!