You may wish to consider if you need to throw.
For reference, a throw reverts every change in the transaction so far. Solidity helpfully continues the reversion down the stack (although there are ways around this). All gas is consumed in the process.
Considering all this, a throw may be overkill if the transaction can be reversed manually. If the modifier is to prevent everyone except the owner from withdrawing money, there's not much need to undo the transaction. If the modifier is to prevent people from depositing money, then it makes perfect sense to throw.