This was a pretty bad example cited in the article, where the incident basically lost Citi a customer (who was previously considering expanding his relationship with the bank):

"Before the debacle, the 32-year-old software engineer in New York City had considered moving some of his savings to Citi’s wealth management division to take advantage of a discount on the Strata Elite’s fee. Now he says he plans to close the card before the next renewal date.Soon after his first call to customer service, two other Citi cards he had had for years were also blocked. For now, he is leaving them that way.

“I don’t want to be the one to call anymore,” he said. “They can block them if they want, I don’t need them.”