I don't know that anyone has brought up the brashness of this whole thing. DL is collecting fuel surcharge for partners that don't even charge a fuel surcharge. How is this anything other than a complete and utter rip off?
As with the fuel surcharge threads have pointed out, it's just a way to increase your income, and is not really tied to the extra cost of fuel. It's not like, "Well, we figured fuel at $75 a barrel, it's $135 now, and the difference for this flight is $45 per person".