I am a caffiend. It is my chosen vice, as I don’t drink, smoke, or partake of controlled substances. My other vice is hot, hot ladies, but I’ve found they’re harder to obtain than caffeine-laden beverages. However, both are often found in the same places. So I’ve got that going for me.
     I also pride myself on being a fountain of useless knowledge, but recently my caffeine knowledge has been called into question. I have found most people are very confident about their caffeine knowledge (including me), but that confidence is almost certainly misplaced. This is because most information on caffeine is obtained “tribally”; in other words, it was passed on by word of mouth, and I have found that key details are often missing, and assumptions are being made. Again, I don’t exclude myself, so I’m here to show my useless knowledge is at least correct.
     One of the big problems is that we might not be talking about the same thing. For instance, there are several charts explaining how much caffeine is in a substance. However, they often make no mention of the amount used for the test, or normalize the results (i.e., list mg/fl. oz.). At home, we might use 8 oz. (1 cup) for coffee and tea, but most coffee shops won’t sell you less than 12 oz (bless their hearts!), and some caffeine listings give a serving as 6 oz.. More to the point, it has been shown that the same person, using the same equipment and process, will have varying amounts of caffeine in what he/she brews! If you’ve ever tried to consistently measure a teaspoon of tea leaves, this makes a lot of sense.
     I’m particulary interested in espresso vs. brewed coffee, another area rife with disinformation. The difficulty here is in getting consistent numbers for 1 serving (shot) of espresso, which can be 1-2oz., so we’re already off by up to a factor of 2. The charts I found list espresso as having more caffeine per ounce than brewed coffee, although I have read previously they are equal; I can’t find that site now. But it also seems consistent since you get so much more brewed coffee in a serving, it can be more potent. Most of the data shows that a 16 oz. brewed coffee will offer more caffeine than a 16 oz. latte, with 2 shots of espresso. Another factor (not mentioned in the reports), is that you’re also getting 12 oz. of milk in that latte, which could slow the processing of caffeine.
     Perhaps the most widespread misconception lies in coffee vs. tea. All charts I found show tea to have less caffeine than coffee (about half). However, most people I know believe the opposite, which is particularly ironic since they’re very bright, and most of them are scientists or engineers who pride themselves on being well informed (and if they read this article, they will be!). Now I’ve always received a much bigger jolt from coffee, and I’d think this would be obvious to anyone, but maybe believing tea has more is having an effect? I wouldn’t be surprised. I did find tea has two other chemicals in the caffeine family, but they are negligible. Also, tea does contain actual caffeine, not a caffeine analog called theine, as was once believed (even by a chemistry PhD friend of mine).

Hope that clears things up a bit. Here are my resources:

Adagio Teas (great vendor, BTW)
Caffeine FAQ
Wikipedia
How Stuff Works