Why doesn't a stripped/cracked MagSafe power cable shock?
Magsafe cables only carry voltages ranging from 14.5 to 20 volts, which is not nearly enough to be able to feel. For more information, see this Electrical Engineering Stack Exchange question. You would not be able to touch the actual conductors anyways as the metal "wire" that is visible in this picture does not carry any current, as it is just shielding around smaller insulated wires. It is unlikely for arcing to occur, but you should still get the charger replaced soon. Like iPhone and iPad chargers, always buy MagSafe chargers from an Apple Store or the Apple website as ones bought on eBay and Amazon are known to be non-UL listed counterfeits.