Usually a cap is employed to keep charge long enough to write to an EEprom or solid state, not to perforem the memory itself. As stated, most now employ small lithium batteries lasting five years. As for mischief, while these small batteries did not have "shock" value, sticking two of them together with reversed polarity and dropping them in someones pocket used to provide amusement, but as always someone took it too far and dropped one into a molten solder pot, exploding and spraying solder all over everyone.
People wonder why we have health and safety overkill thee days !