Flew on Sunday on NW380 ORD-DTW-BOS.
Early in the morning I had an interesting phone conversation with a reservation agent about this being a direct flight about getting an upgrade for the 2nd segment (where seats where available) while there are no seats on the 1st segment. The agent said she cannot break my flight although it's a chage of plane flight.
So much for breaking the flight - the segment ORD-DTW landed at gate A72 while the DTW-BOS departed from A1... NW should credit me with that extra mile of terminal tram!
Also, I saw the passenger count on the flight - ORD-DTW 140, ORD-BOS 1(ME!). In other words - someone who wants to fly ORD-BOS and doesn't care much for NW/KLM miles would probably take UA or AA.

Great marketing trick, NW!