yes, fast charging will hurt your battery. Doing it too much will hurt it all the faster. Using a battery is not what damages them, it is the charging and allowing them to sit uncharged that damages a battery.
Charging holds different levels of ability to damage your battery. The faster it charges, the higher the wavelength which is used to charge. The higher a wavelength, the more rapidly it deteriorates. Higher wavelengths also occupy more space which means your battery charge will not last as long being fast charged. Lastly, the higher a wave length, the more heat it brings with it and heat is always a bad thing for electronics.
The proper way to charge any battery is in the slowest possible way which uses the lowest possible wavelength. This both makes that one charge last longer AND makes the life of your battery longer. (Cf Ron Hobson)