@Nexox and Francis
"So Apple is fudging that safety factor in order to make a 65W power supply that's smaller than a Dell or HP 65W power supply. And that's the sort of thing that leads to people needing to call the fire department..."
Well if this is true, then why is my 90 watt HP laptop adapter smaller than my wife's 85 watt Macbook Pro adapter?
"The solution is to use a proper connector design, and to select a cable that is fit for purpose. It isn't as if these are new issues in the annals of electronics design. Talk to the nice guys at Belden about the correct specification of cable (for instance shielded twisted pair, and a shield that isn't braided) and design a connector with real flex control at entry."
I agree about the strain relief troubles with Apple adapters. I've had more than two adapters fail from this same problem. However, I will disagree with your comments that braided shielding is inappropriate. As an audio technician, we've always been trained to use cables with braided shields when the cable will be moved frequently. This is because the solid foil shielding (the only alternative that I'm aware of) breaks down very quickly when it is moved, whereas the braided shielding tends to fare much better. My personal experience has verified this claim. We've had foil shielding fail after the cable was only lightly moved once or twice, but we have braided shielded cables that have been in use for many years without any failures yet.
However, the point that the shielding should not be supporting the electrical load is well taken. In my (non-electrical professional) opinion, it would be best if the shielding was grounded, but with a separate ground/common wire running within the shielding to carry actual electric load.