They'll just charge your shit anyway. That's how they are. Watch them go through your transaction history and track down your CC number.
I AIN'T FALLING FOR YOUR TRICKS, SONY.
What happens if I have insufficient funds in my Sony Entertainment Network wallet?
If you have insufficient funds in your wallet but have Automatic Funding enabled, we will charge your nominated credit card. If you do not have Automatic Funding enabled, and have insufficient funds on the expected payment date, your pre-order will be cancelled. If you do not wish to use Automatic Funding please make sure you have sufficient funds to cover the cost of your pre-order in your Sony Entertainment Network wallet on the payment date.
from the official Playstation website:
http://uk.playstation.com/ps3/suppo...n-Store-pre-order-frequently-asked-questions/
Edit:
ok, so I'm still downloading, but I did just got a message that my PSN account has insufficient funds.