Never heard of it until today. > Spark, which launched in July, is a social feed of photos. It is similar to Instagram, but open only to Prime members. There

Never heard of it until today. > Spark, which launched in July, is a social feed of photos. It is similar to Instagram, but open only to Prime members. There is the reason--thinly veiled way to encourage people to buy Prime. Facebook succeeds because "everyone is there." Not everyone can afford Prime.