Google+ have tried to solve this "noise" problem through the ui with a "volume" slider. But it's like fine tuning a recording desk if you have to do that to 50 circles to get the mix just right.The problem is, that's not even the right approach. It's built on a faulty assumption - that "who" is the sole determinant of whether or not I'm interested in something. That's not even close to true, unfortunately. I have plenty of social-network connections for whom I value their posts on certain topics and have less-than-zero interest in what they have to say about other things. For example:
"I follow Bob, and I want to see Bob's posts on technical topics, but NOT Bob's posts on religion."
Or more generally:
"I follow all these people, but regardless of who posts what, I never want to see pictures of cats."
I'm just not sure it's solvable through the UI and that we may have to be quite harsh on what "noise" we let through and rely on "if it's important enough, it will find me". There's just too much data to consume otherwise.
I don't know, I think a solution that was 80% effective would be incredibly valuable. I don't see this as something that's "all or nothing."
And my personal take is that, in the case of G+, the Circles thing is a good start, but they need a way to specify "excludes." Whether those excludes should be explicitly defined by the user, or whether they can use machine learning to figure out what I don't want to see is an open question, granted. But I'd take some UI for specifying "exclude this topic" (while acknowledging there is some inherent fuzziness in this) in the meantime.