In my games i make players count ammo. I think it helps the realism with the game, and like was said, even Legolas is short of arrows sometimes. It is cool when they are short of ammo and start thinking about if they must shot or not. And its fair, if you make the dagger thrower get 10 daggers, you must make the arrows ends too.
Any people with proficience in bow and crossbow can make 1d6 extra arrows in a day of adventure most of the time.