It's not welded in. There's a tray for the SIM-card. It was clearly shown during the keynote.
Ok, that's good. I was starting to freak out a bit. It's the long slot we see near the top on the side of the device, right?
http://www.apple.com/iphone/technology/specs.html
Hmmm... Silly question, but does anyone know whether a BlueTooth-enabled, 3G phone could be used as a modem for the iPhone (the way some phones can be used as modems for laptops, I mean)? It seems like that could be a way of adding 3G to the iPhone for people who really need it. Or the ability to connect the iPhone to the internet in a zone that only has CDMA networks. It's complicated, yes, but it could work with a bit of hacking, right? Maybe?