Originally posted by SyntheticGerbil
Well okay, maybe I'm wrong. It's funny they would need your credit card for a preorder if they aren't charging you.
1st: It's convinience. How would they tell you they need your credit card number when the game is out? If you don't check your e-mails regularly, you might not get the notice, and many other things.
2nd: Check your credit card statement. If they charged something, calll EBGames up, and complain.
Vader's wife was very pregnant when she died 19 years ago. All of a sudden a 19 year old who is very strong in the force and has a distinct resembalance to him in his younger days rolls in from Vader's home planet with his old Master Obi-Wan (Who was the ONLY other person preset at the time his wife died. And to boot, the kid's last name is Skywalker.
So in answer to your question, he knew Luke was his son because his name is Darth Vader, and not Darth Retard.
-Forum post on why Vader knew Luke was his son.