Bought an iphone 3gs that wasnt activated. Upon attempting to activate with my at&t sim, Itunes asks for zip code and 4 digits of Social Security. I was not the original purchaser of the iphone and i cannot reach the guy who sold it to me. Any way i can get around this?

Did you buy from a person or from the Apple Store? If you bought from Apple, just go to the genius bar and they'll make it work. If you bought from a person, you really can't get back in touch with them and you're using AT&T, call AT&T and work with them to get the device activated. If you can't work with Apple or AT&T, you may want to hacktivate (depending on firmware revision, etc.).