As activity streams become a key part of more sites (it is now our home page) it would be useful to have the ability to hide particular items so that they don't appear on it.

For example, if I bulk create a number of events, I could hide all but the most relevant so as not to flood the feed for everyone.

How would you measure 'relevant' or identify the items to show or hide in the activity stream? 

It would be a manual decision - I'm picturing an additional flag against an item alongside feature/pin/etc.