toothbrush or underpants

When the internet came into our lives, strongly, about 15 years ago, my wife said something I often think about, maybe because it says something about marriage, too. Everyone was getting email accounts, and she said, "Is email like toothbrushes or underpants? Can a couple share them or not?" I don’t think that issue had been worked out yet, socially. Though she soon recognized the convention; it was like underpants.