Acoustat, You're right of course!
But, then again I found that killing first side reflections with 7ft bookcases filled with stuff worked just fine, as do wall hanging tapestries, or acoustic foam. I've also found that plants in front of glass windows can act as excellent diffusors, just as drapes can act to deaden sound off the wall behind the speakers, even if there are no windows behind it. Hell, you can even hide acoustic foam behind light curtains so you will not communicate your audio affliction to your unappreciative friends. Depends on your actual needs by virtue of room acoustics, set up, and of course speaker design.
FWIW, I'm still trying to figure out how to put bass traps on ceilings or to kill the cathederal effect of high vaulted ceilings, or for that matter flat lower ceilings unless your decorator allows you to install fake support beams on the ceiling to break up the first reflections off the ceiling. I don't think I could get my decorator to allow me to plaster my ceiling with acoustic foam.
Now if I didn't have others to consider and no budget constraints I would use RPG diffusors, acoustic foam deadeners, and, maybe, bass traps if I thought they would solve a problem I was experiencing in the bass frequencies that they affect.
The only thing we disagree on, I think, is you statement that "all surfaces need treatment". There are highly reflective surfaces in a room which are, as a pratical matter, meaningless so long as the frequencies they reflect efficiently are blocked on the surface that recieves the reflections. Simply put, for reflection control of 2d reflection points you would only have to treat alternating walls, not every wall, the floor, and ceiling. Sort of like live end/dead end room set up, sort of. Anyway thats my take on it. I'm just a Newbee, in acoustics anyway. :-)