On the Xbox 360, you can't use the Netflix app unless you are an Xbox Live Gold subscriber. Granted, you get access to all kinds of other stuff by going Gold, but if someone is asking about purely using it as a Netflix playback box, without knowing anything else, you have to attribute the $60/yr cost to that.
Ah yes, you're correct. I forgot about that. Thanks for clarifying. Come to think of it, my gold subscription is coming due this month...