Yesterday on sansmirror I wrote an article where I used the following statement: "[no] camera [exists that] allows me to get to great images without any friction." Today we get an interview by Rob Galbraith with a Nikon engineer that allows me to show my concept of design friction at work.
Basically, the D4's new battery and charger solve frictions that Nikon themselves have: they need to comply with new Japanese regulations (size of battery) and don't want any liability (chance of problems using new battery in old charger and vice versa). The result of those frictions to Nikon is that they changed the battery and charger designs to be incompatible with older versions.
This introduces a customer friction: a pro user now has multiple batteries and chargers if they have a D3s/D3x and D4, and they have to buy new batteries and chargers, which is a cost friction. (According to Nikon, but unverified, there is no real images-per-charge friction introduced by the change; I'm doubtful of that assertion, especially in certain usage scenarios, but I'll reserve judgment until I can check it.)
This is exactly how frictions shouldn't be resolved. It's fine for a company to remove frictions in their manufacturing and costs, but not if they introduce customer frictions. It's fine to reduce customer frictions even if they increase manufacturing and cost frictions to the manufacturer (within reason, of course).
Nikon got it backward. Let's hope that's the only friction they increased.