Tanenbaum pointed this out a couple decades ago with respect to AT&T:

At one time, 80 percent of AT&T’s capital value was the copper in the local loops. AT&T was then, in effect, the world’s largest copper mine. Fortunately, this fact was not widely known in the investment community. Had it been known, some corporate raider might have bought AT&T, terminated all telephone service in the United States, ripped out all the wire, and sold the wire to a copper refiner to get a quick payback.