Yes and no.
You can't really term Caffeine as "bad for you" and you can't term it as completely safe.
The key is always moderation and age.
Taking too much caffeine can have very bad negative side effects, including insomnia, over active Adrenal glands, negatively effecting your metabolism, headaches, excessive sweating, addiction & uncontrollable shaking.
You can also damage internal organs by taking too much over long periods of time. Caffeine is filtered through your kidneys, which also filter many other substances. So if you do take lots of caffeine you have to be careful about other substances that could cause your kidneys to overload and completely shut down.
Now that's all very extreme.
Typically a small amount of caffeine per day, 70-80 mg or 1 cup of coffee is perfectly safe. In fact, most people can handle around 400-500 mg per day without any issues.
Some people are more sensitive to caffeine than others, and so they have negative effects at much lower amounts. It's completely different for each individual.
Also, age is relatively important. Since your adrenal gland is part of your endocrine system, which regulates hormones, you really shouldn't stimulate your adrenal gland too much while young. It can cause negative things to happen, including stunted growth & hormonal imbalances.
Again, that's pretty extreme, and would only happen if you're REALLY over doing it, but just to safe, you shouldn't really drink much caffeine (less than 200 mg per day) until your 18 or 21.
At that point, your system will be more ready to handle the shot of adrenalin that you'll be getting from caffeine intake.
Just as a side note, here's a pretty good place to find out how much caffeine is in most energy drinks
or other supplements here will list caffeine content.