How was it being charged? If you were using a usb port, a car charger or lower quality wall charger I can see how that can happen. Its possible with the stock wall charger but it is a lot less likely.

 

what's even worse is when you try to navigate with a low battery and the phone dies, while charging!!! It's occurred several times to me. I hate when that happens.

 

In some cases even plugged in you can kill the battery. The phone can use more power than the charger can give it.

 

my droid 1 if you played videos it would drain the batter when charging.

 

Also depends if you're using cheap USB cables. I bought a Sprint Mifi card and it came with a big fat cable that had no problems charging, and seemed to charge faster than my regular USB cable. Are you using your stock cable?