I own a macbook 2012 and the cable snapped due to strain relief. I have not wrapped the cable around the charger box tight considering this could happen but it did anyways.
Is this covered by the warranty?
This happened to me as well. Because my computer was more than 1 year off the shelf, it was out of warranty; they charged me $60 rather than the $80 shelf price for a new Magsafe charger. Hurry to Apple Church before your warranty expires! Their Support page for this: http://support.apple.com/en-us/TS4127