Here is the thing. I think that following posters primarily, as opposed to subjects, leads to the best content and the most thoughtful conversation (premise: That's what you're looking for). But I think we have to realize that subjects matter too. People want a way to get at their content related to cars, coffee, Apple, poetry, -whatever.

Right now, we follow those topics by proxy by following people who care about them. In doing so, we get some cool serendipity when those people link or talk about topics that deviate from their main, reliable interests. And we get good convo and discussion when they stick to the reasons we followed them in the first place.

Tags are a hack to get right to the content we thirst for without an intermediary. It's so natural to want them or something like them because of the immediacy. So we've got this balance where we get higher quality content by proxy but overwhelming immediacy by 'tagging in'. Right now Hubski has both, with following people as the obvious main route to content in your feed, and a stunted version of tags second. I think tags are a WIP and still need to be figured out, but should remain always secondary where they can be experimented with as time goes on. Removed, pluralized, mechanized through voting, etc. Whatever. The functionality of the immediacy of tags hard to argue, but so is the degradation in quality that comes with them as sites scale. That being said, I think there can be some innovation around them as long as they keep a secondary role.