The Merc article pointed out that credit cards were not the big issue here. One very significant one was medical bills that were assumed to have been paid by insurance but were not.
Having experienced the volumes of paperwork received from hospitals, doctors, surgeons, anesthesiologists, nurses, and so on for a two day hospital stay, two ER visits, and an outpatient surgery, I can believe that people tend to assume that the insurance is taking care of it, but that may not be the case.
I had to make several calls to the hospital billing department because they kept sending claims to the wrong insurance company. I was only aware of this by actually reading every stinking bill and realizing that something was wrong. It would have been easy to have had two very large bills drop to collection before all of the billing and insurance negotiations had completed and I saw that the hospital still wanted a few thousand dollars.
The article made it clear that many people were totally unaware of the debts, often lodged in error to someone with a similar name, even existed until the first contact from the collection agency.