I assume he is talking about Visa/Mastercard gift cards. If so then they do not need an SSN number to work online. At least here in the USA. You can pretty much enter whatever information you want.
Hmm, the last time I tried one, bought with cash at a 7-11, I needed to go on their website. and enter a lot of information before I could use it online. Are the gift-cards something else? Maybe I am just recalling incorrectly and SSN wasn't one of the things they asked.
They don't in the UK either, sometimes you need to register them (and supply the same info when purchasing) but you can put in whatever info you want there...