Google plus, filtering and moderation.

What G+ needs is the ability to filter comments by rating.

Not so much for the viewer, though admittedly it will get used in that way if available.  But for the poster.
I'm thinking particularly for the Scobles and Days who will often generate hundreds of comments for a single post, especially one that's asking for feedback.
What are they to do: wade through the entire set?  Read the first few, read the last few?  Ideally, they'd like to cut through the chaff and just peruse the most worthwhile comments.  And we have a system already in place for that - it's the plus one button.  Arguably underutilised on comments, but nevertheless it's a good first step to giving the poster a filter to place over a moderation system.
The problem with allowing it to be used by viewers is that they'd also want to filter out all the nonplussed posts.  But if they do that, then very few posts get plussed, certainly no new ones after the first few have been posted, and the ones that are plussed already will just quickly gain more (they're the most likely to be seen).
So in order for the system to work viewers of other people's posts probably shouldn't be allowed to filter.

What does this mean for people who follow high-profile posters such as Scoble and Day?
Reading a post 12 hours after submission means there are already several hundred comments.  Without a filter they're in the same position where they are now: reading the lot, the first/last few, or none at all.  Cue the comment: "I haven't bothered reading the other 300 responses, but here's what I think...".  In which case, why do they bother, and why would they expect anyone is reading what they've just written?
Harsh as it sounds, I think the only solution is for viewers to be given the unfiltered view so they can read through (some of) the comments if they please and moderate appropriately, or just post as if they're the only commenter there.

But note that in this situation the viewer is of secondary concern (they've read the post, they've possibly offered feedback).  It's the poster who's of primary concern, since they've posted and would like, in the case of excessive feedback, a summary of responses.