Most of the article seems critical of the diamond industry. Have they not done people a service by providing them with a nice product that they can enjoy?

There are certainly moral problems with how they built their empire, but why are clever marketing and aggressive pricing bad things? The former is simply how you tell people about new products. Remember diamonds went from being owned by almost no one to being owned by lots of people. If those rings make them happy, then why is it our business?

How is DeBeers marketing any different from Apple marketing?

Of course, the article does do a good job in warning people that their diamonds may have little resale value. But that's a risk most buyers are willing to take. After all, most non-divorced people don't sell their wedding and engagement rings.