E-commerce advertising. I worked at a company that managed online advertising (mostly Adwords at the time) for ecommerce companies. Most would provide us with a

E-commerce advertising. I worked at a company that managed online advertising (mostly Adwords at the time) for ecommerce companies. Most would provide us with a CSV with all their products - this would sometimes be hundreds of thousands of entries. We imported enough CSV (gigabytes a day maybe) that it was worthwhile to do things like implement custom CSV parsers to deal with some of our larger customers noncompliant CSV. JSON might have been nice, but I can imagine it coming with its own trouble as well. CSV worked well since our tools would allow analysts to interpolate columns into the copy or key words when doing bulk ad creation. The nestable nature of JSON would have complicated the interface given to our nontechnical analysts. I also imagine many of our clients wouldn't even know what JSON is.