My take on this is simple: many competitors (Hulu, Amazon, Verizon, Comcast, etc.) are likely using the API or screen scraping services like Instantwatcher to gain critical competitive data about Netflix's catalog size and composition, deal term length, content popularity, etc. With the former dataset, you could basically build a list of average contract term length, suppliers, genres, popularity, etc. What leads me to believe this is the case is they first killed expiration date - obscuring when titles expire makes it difficult for competitors to pick of your best stuff. The recent changes probably came after Netflix took a closer look at how the API was being utilized.