[originalgeek]

You are making an assumption that PSN is not storing the CVV code, and may be incorrect. Though PCI guidelines explicitly forbid storing this field, there are some who flout the guidelines.

To answer your question, it is similar to places like Starbucks, that do not require a signature when you make a purchase. In such cases, the merchant has cut a deal where they agree in advance to accept all chargebacks without dispute.