I suffer mild withdrawal if I stop drinking tea. I might get cranky and maybe get headaches, but mainly my brain kind of shuts down a bit, like being too hungry. And in fact caffeine, like other stimulants, is a fair substitute for food for a while too.
So I structure my work day largely around making and drinking tea. Some of the reward is just drinking a nice-tasting hot liquid, especially in the winter (and that feeling might even be a little addictive too). At a workplace some of it is going to the kitchen and chatting with people. Some of it is caffeine.
But the surest measure is that as a society we've spent a whole lot of money making sure no one need ever be more than a half-block away from a sure source of roasted and ground tropical beans, and we continue to fund that expensive effort even when we don't actually own our houses any more.
Fortunately it turns out the stuff's mostly sort of good for you, and though it's not cheap it's even kind of vaguely socially positive if it's the fair-trade organic stuff (which is basically all you can buy around here nowadays).
I don't know of any statistics on how many people are addicted to caffeine, but I did find that about 90% of American adults and 76% of American children consume some form of caffeine every day. And since experts say that even just one cup of coffee per day, if consumed regularly, can result in withdrawal symptoms if you stop, I would guess that caffeine addiction is extremely widespread.
Not very surprising, considering all the coffee shops, energy drinks, and other sources of caffeine that have become commonplace. Luckily, like indreams noted, caffeine is rarely dangerous and even has healthful properties.
Click Here to search for a treatment center in your state that is right for you.