[C00LSH33P]

I think he's talking about the National ID numbers.(not a code lol) Well, last time I checked there is nothing anyone can do with that numbers of yours, really.(Maybe not, as different countries is different) If otherwise, then we all would be f*cked by now. Unless, someone stole the physical card or you used that numbers as your steam account password then uh-oh.. bye bye sweet inventory.

[Powerlord]

My national ID number (Social Security Number since I live in the US) is private kthx. My driver's license number is kinda/sorta private, but not really.

[claudiuhks]

It's called Photo ID number. It's generally a personal information such Passport or Driving License and shouldn't usually be published.
The regulations differ on almost every country and generally no one can do anything by using your ID number.

More info is provided on Wikipedia and it's free. Why don't you just read that?

People searching for others' IDs are intending to create fake accounts on variety of companies such PayPal(tm) and they need a picture of the Photo ID. So, a picture does not mean a number.

The PayPal(tm) European regulations automatically close accounts having a negative balance and directly contact the account's holder to take the money back. If the Photo ID is yours then you will have to pay that.