How much caffeine is too much?

“For regular coffee drinkers like myself, a hot cup is a must-have in the mornings to really wake up. A lot of people don’t realize that other things have caffeine in them also, like soda and chocolate. To find out how much, see the chart below.
If you don’t take too much, caffeine makes you alert and helps you concentrate. It also reduces headache pain and may postpone exhaustion.
Too much caffeine makes you feel anxious, light-headed, jittery and irritable. If you really overdo it, you may even get diarrhea, unsteady hands and an upset stomach. Caffeine may also make it harder to get to sleep. I personally drink about three cups of coffee every day. Just don’t over do it.”