Is I bad if my iPhone charges really fast?

I know it's a silly question because it's obviously a good thing if it charges fast, but every minute or so, the percentage of the battery increases by 2, for example, if the battery is at 30% at 2:00, then at 2:01 it would be 32%, and so on. I want to know if this directly correlates with bad battery life, or if it was made to charge fast. Btw, I have a iPhone 4s, 16gb on iOS 5.1.1

Watch out, it could explode

Your in the phone charger is now corrupt, the battery will soon be history, and so will the phone.
The battery could still explode.

Might be the charger, and your phone or battery won't be harmed so long as the current thats going into your phone isn't more then.1A or 1000mA, anymore then that would corode your battery and render it unless. I charge my Evo 3D at.85A or 850mA.