The MagSafe connector is a true improvement for notebook users, as it prevents notebook to fly from a desk because the user or a third-party got stacked into the power cable. However, the magnet of the MagSafe could make the cable more "fragile", and Apple released two TechNotes explaining in details on how to (
reduce cable strain on your MagSafe power adapter) and how to
How to disconnect the MagSafe power adapter)

If you see your cable twisting without any reason, this is mostly due to the metal wire inside, so contact quickly your Apple Reseller as many users have seen their MagSafe starting burning or smoking due to excessive strain applied to the cable (especially for MacBook Pro Core Duo).