Actually, cocoa contains theobromine - a similar, but different chemical. Both of these are related to caffeine. The Hershey website confirms that Hershey's cocoa contains 108 mg of theobromine per teaspoon.
Although theobromine is very toxic to dogs, it is much less so to humans. The lowest reported toxicity level reported for theobromine is 26 mg/kg of body weight. So, for a 150 lb (68 kg) human, the LOWEST toxicity level is 1772 mg (over 16 teaspoons). There is no LD50 level (dosage at which 50% lethality occurs) available. I suspect this is mainly because theobromine toxicity in humans is quite rare.
Theophylline is actually found in black and green teas. So, perhaps one should watch one's intake of them.