This worries me as a customer. As a consumer, having access to other interfaces, even if I'm not using them, seems like better value than however Netflix thinks they can monetize their customers' viewing data. If they do find some other income stream, maybe they can use it to keep pricing flat or buy more content. But after the Qwickster debacle, I'm not too confident in their ability to do this. Discouraging other enterprises from building businesses around them isn't a good signal. If Netflix drives itself out of business, I hope someone else (Amazon perhaps) will pick up the lead. I really have no interest in getting a cable subscription.
I'm curious as to why you think a company discouraging a third-party from building a business around them isn't a good signal of the survivability of the company. Are you implying that Netflix needs these third-parties in some way?
I would imagine that the vast majority of Netflix's customers not only do not use this third-party app ecosystem, but that they have no idea it exists.