Guessing that the Account was compromised or you gave the login details away, and you had to contact Support to get the Account back. Obviously, DOB is one of those questions you need to know.
Now, if you had been a brainy person with good intelligence, then you would have put into place a great little security measure that Sony have, and this would have kept your precious Account with all it's purchases safe - the 2 Step Verification.
Nobody, could have stole your Account without first seeing your Handy Phone and the Code that is sent to it when you sign into your Account.
You have lost your Account now, down to stupidity.
This 2 Step Verification process is really a must need for people that make False Accounts.