In military terms, it's switching from a crust defense (the perimeter) to defense in depth. There are situations where the former can make sense, such as a sie

In military terms, it's switching from a crust defense (the perimeter) to defense in depth. There are situations where the former can make sense, such as a siege, where e.g. a penetration is quickly obvious and you can use your interior lines of communications to rush reserves to the action. The key, of course, is the "quickly obvious". Prior to the stats of the art allowing that (which sounds difficult and painful in principle), defense in depth is obviously the way to go. But you've got to achive it in some why where e.g. compromise of "bob@nvidia.com" + password doesn't quickly get you past any defense, or any that's relevant to bob.