How you treat it?
Surely a power cable should be designed to be treated in the way that most users treat them - winding it up and unravelling it every day, and the ocasional yank where someone trips over it. If it can't stand up to that usage, then it needs to be a stronger design.
Those who don't have this problem because their laptoprarely leaves their desk - Isn't the whole point of a laptop to be able to take it (and the power supply) with you?