2. Could someone tell me WHY D.O. is required? Not why the USMC wants to do it, but why anyone would be doing it?
I thought about your question above in more depth as I drove home from work today. As I said above, I'm a little on the fringe when it comes to what Colonels and Generals alike have said about why we need DO, but at the core (and beyond the sexiness) I think the impetus may be an urge to match enemy assymetric capabilities.

Think of Taliban/AQ elements in the Afghanistan context. We haven't done that good of a job running them to ground while lumbering around in large formations. In the current scheme of things, the lowest-level unit capable of extended and independent operations may be X size. Well, we aren't killing a lot of bad guys with X size units, so some probably feel we need to reduce our signature and footprint in order to gain that edge in surprise.

The problem is that while it may have worked okay enough when both antagonists in a conflict were foreigners (Germans vs. Commonwealth in N. Africa...Chindits vs. Japanese in S.E. Asia...etc.) in a strange land, things become a bit more tenuous when the enemy is swimming in the sea and you're nothing more than a fisherman trying to avoid falling out of the canoe. That's why I think we need to have the ability to revert to DO when the time/space permits itself, but we are in for an ass-whoopin' if we want to kid ourselves that that is the only way to go, and we can just aggregate to meet larger threats.