The MagSafe 2 connector fails that balance test. Badly. The magnet is too weak. It’s so weak, it keeps falling out. It falls out if you brush it. It falls out if you tip the laptop slightly. It falls out if you look at it funny. It’s a huge, huge pain.
Can’t say I’ve noticed this with the 15-inch MacBook Pro with Retina Display, but I don’t move that around while charging. Maybe it’s more of a problem with Airs?