Can you answer my other question though? Do both people have to have the same GS3 to use S-beam?
You should be able to beam between any NFC Android device with ICS or later. I use a Verizon Galaxy Nexus; my son-in-law uses a Sprint Evo 4G.
Can you S-Beam to say a Blackberry with NFC or a Razr?
I didn't know, but that's a darned good question, since quite a few Blackberrys, Windows Phone, Android, Symbian, Meego and other devices do have NFC, and most do have a form of Beam as well. (Here's a list of all current NFC equipped phones.)
So I grabbed the specs from the NFC forum. Apparently they all use the "NFC peer-to-peer" communications mode. This is intended for device to device messaging.
So to answer your basic question, it looks like all NFC devices should all be able to talk to each other. But what do they say? Okay...
Over that comm link, the NFC Data Exchange Format (NDEF) is used to send messages for things like setting up Bluetooth or WiFi connections, transferring contacts, data, photos, etc.
Each message type can be a URI, a MIME type, or a custom designator. E.g. if a web URL is sent, then it's up to the receiving device to ignore it, open a browser, store it as a bookmark, or whatever.
So would all phones recognize or do something with all message types from each other? Doubtful, but they could if the manufacturer wanted to. Many probably can share files at least, over a Bluetooth link they set up this way.
Thanks for asking. I learned something new myself!