Apple has published a support document that outlines the procedures of Apple’s adapter replacement program for those who have faced strain relief problems with their “T” style MagSafe power cables on Apple laptops.
“Apple may provide customers a replacement adapter if the power adapter shows signs of strain relief,” the company says. “Strain relief is defined as a condition where the DC cable (the thin cord that attaches the MagSafe connector to the power adapter) separates from the end of the MagSafe connector or from the other end of the thin cord, at the power adapter.”
Read more about the adapter replacement program at http://support.apple.com/kb/TS4127 .