Why is it called MagSafe?
The magnet can save your computer.
Let's suppose it's on a table connected to AC. If someone pull the cable with his foot by just walking by, the MacBook won't fall on the floor, the magsafe will just pop.
This is well answered by Wikipedia’s article on MagSafe.
Summary: to obviate expensive repairs to connectors and laptops when users tripped over their power cords, Apple designed a connector that would stay connected mag-netically under normal circumstances, but which would safe-ly disconnect when the power cords (or laptops) were suddenly pulled away.