I recently found the most informative literature on caffeine that I have ever read.  I was "Googling" to try and figure out how many miligrams of caffeine are in a cup of coffee to compare it against energy drinks, and look what I found!... all sorts of surprising information on caffeine that concludes that in fact, caffeine is a drug.  Below are some exerps, but you should definitely read the whole article - for your own information:

http://www.xs4all.nl/~4david/caffeine.html

"Caffeine is the world's most popular drug"
think about it...

"Caffeine-caused tremor can reduce hand steadiness."
ya think?!

"The lowest known dose fatal to an adult has been 3,200 mg - administered intravenously by accident."
um... caffeine can kill you???? yes.