Me too. I noticed that hubski's mechanics can aggregate focused content for its users too. But it seems to require effort on the user's part to teach hubski how to do that.
Yet I can imagine user's starting what are essentially the equivalent of subreddits by creating accounts with usernames such as "popmusic" and more specific ones such as "1975 Chevy Impala". Of course under the influence of a single person those "users" would probably not be as good as a properly moderated subreddit.
Hubski's tag system combined with following specific individuals is probably a better way of staying up-to-date on a particular subject, though.