I plan to take just about everything not nailed down, but not necessarily steal from people. If I find a raider camp and kill them, then I will take what I find, same with any random building. I expect the things to have weight. It sounded as if building material to build your settlement would not add to your carry weight, and with that I will try to be selective in what I dismantle for my settlement. From what we saw at E3 it appears there are 10 different settlement locations or building types.
Anyplace I decide to set up, the surrounding area will be picked clean of smaller crafting items, but I may leave other building elements alone provided I have what I need to build a base, and the surrounding buildings don't impede my defenses.