It is time to promote my idea 
Block annoying users from activity feed : View Idea
Hiding all such users' activity from activity feed would give you a better view of activity feed.
This user specific blacklist would be used by SCN to decide what goes into your activity feed.
If this idea is implemented, in future SCN can use the blacklist as one of the signals to decide the trending score of a user.
You might also want to look at my blog which talks about a client-side way to hide profile pics of blacklisted users.
Block profile pic of annoying users on SCN
I love the blacklist tv show primarily because of the lead character.
I don't think having an intermediary matters so much. It just helps you exercise control. What matters is to stay relevant by withholding information.