Requirements for a filtering header

There has been discussion back and forth on different aspects of this 
problem. At this time, I want to get a feel from the members as to:
1. If there is a rough consensus that a standard filtering header would 
be useful.
2. If there is a rough consensus as to what issues need to be solved for 
such header to be useful.

If these are satisfied, than I would like to ask for some folks to 
volunteer to write up a requirements draft from which we can continue 
the discussion.

Yakov