Netflix Turnaround Prediction Calculator

M. Villanueva has written a nifty little web page that estimates how Netflix will possibly alter your future shipments based on whether you've rented too many movies and need "punished".

Personally I do see a line where it becomes unprofitable for NetFlix with their shipping charges, but if you market a service as 8-at-a-time and someone gets the discs back in the mail next day (maybe multiple people in the family watch only certain discs) you should certainly be able to cycle through more than 40 discs in a month (not accounting for odd mail holidays and rural routes).