That looks to me as smart way to earn some aftersale money. Notice that it's not MacBook that's breaking so it's not sending wrong message that they break often. Charger is still nothing compared to price of whole set. Third party chargers I'd assume are detected by ton of electronics inside MagSafe plug and motherboard and charge slower or not at all. Bonus points: for cable breaking you can always shift blame to customer "bad handling".
Third party chargers are aggressively pursued with the MagSafe patent. One company made external Mac batteries by buying up Apple MagSafe chargers and chopping off the cable and STILL got destroyed by Apple's lawyers for "violating" the patent.
