The cause of front tires wearing out so fast or wearing out unevenly are things such as too high or too low air pressure, lack of rotation, improper wheel alignment and bad suspension.
When you have too high of air pressure in a tire the tire can wear out in the middle and when you have excessive toe in on the wheel it can cause the tire to wear out in the inside and excessive toe out can cause tire wear on the outside of the tire.
If your tires are wearing out too fast and unevenly then I would make sure you have the proper tire pressure and also have the wheel alignment checked.
You tires could also be out of balance as well.
Bad shocks, bad struts or even bad wheel bearings or bad ball joints could all be causes of front tires wearing out faster.
The actual cause of the tires wearing out fast depends on how and where the tires are actually wearing out.