It seems that Netflix is running a survey again asking whether a Netflix streaming service for the PlayStation 3 is viable. The survey states that a $9.99 Netflix Instant Streaming Disc would be required to run the service on the PS3. We are guessing that it may be a Linux LiveCD disc with a Netflix program - wild guess here.
Here is the most current Netflix survey with the PS3 functionality:
Here is a survey from last year. Notice that the Netflix disc was only $3 and they had 5000 less movies for Instant Streaming.
[Source: Sony PS3 Modding - Homebrew, Upgrades, Mods, and Hacks]