I think it would allow for more specific conversation if there was a way to post something in a way that it only appears to people following the tag you post it to, and not to people following you.
A good example would be very technical discussion of hobbies, which I think Hubski would benefit greatly from, but only seems to happen deep inside of comments of unrelated posts.
Say I posted a question about Archery and wanted to know whether I should buy a compound or recurve bow, or even more technical I wanted to know whether I should use orthographic or perspective projection, or should I use GL_ModelView?(Actually something I'm confused about now if anyone has experience with Open GL), people won't want that sort of thing on their feed so I don't ask. But if there were a way just to post it to the programming tag I wouldn't have to worry about my follower's feed. Plus people might be more likely to follow tags this way.