On Twitter, I tend my feed somewhat aggressively, following folks who post worthwhile stuff, unfollowing those who devolve or who drop below some signal-to-nose threshold.

On Usenet, there was always the killfile and thread branch pruning (although the dedicated could somehow just create a new id, I suppose).

My takeaway being that it should be possible (or easy, even) for a user to shape their experience.

If we were designing a new community, which I guess we're not. :-\