Netflix has been successful in using all possible PR channels available in the market. Their focus is to make more customers aware of their existence and services they provide. Usually promotes through television advertisements, online ads, newspapers.
Till date, Netflix has been consistent in only one promotional activity and that is 1 month free subscription. For those who like watching unlimited movies, 1 month free subscription is more than enough to validate if the services are worth it. Although their catalog of movies appear to be stale in few months of being customers (because they get very few high rated/new movies), most of their customers subscribed for 1 month free service get hooked up for quiet sometime. Therefore, they constantly focus on getting new customers.
Their PR activities are geared towards people at the top of the funnel, customers who have never used Netflix before. Once you unsubscribe from the service (or stop using the service), they do not promote these old customers who have left in an effective way. Moreover, they also do not promote the new offers to their customers who are already using the service.
Once customers have exhausted the catalog and cannot find any good movies, they usually drop off from the service and start using other competitive services such as Amazon or HBO. They do not focus at all in getting their lost customers back by promoting them with some offer. This is what they should focus on, in getting back their old customer who have left.