Let me try to clear up some confusion here.
SIM cards have nothing to do with the technology the carrier uses. It has more to do with the carrier's choices.
CDMA carriers, for example, can use R-UIM cards (basically
SIM cards), but the
CDMA providers here have chosen not to support this feature. Thus, save for their dual network (world) phones, most
CDMA phones do not use
SIM cards. As to the
Storm, specifically, it is a dual network device. It has the hardware for both
GSM and
CDMA. It can use
SIM cards and it can be use here. I know AT&T and T-Mobile customers that use it. How? Simple: they unlock the device. Unlike most other dual network devices that VZW carries, the Storm is a quad-band
GSM device and therefore can be used on any
GSM carrier worldwide. It just has to be unlocked.
As to a VZW
SIM card, they do have them, but they are strictly for international roaming and are locked to Vodafone's network. VZW's non-dual network phones do not use/support
SIM cards. They don't even have a
SIM slot, so there's no place to put a
SIM. Given these two facts, bringing a G1 to VZW or Alltel is futile. Neither carrier has
SIM cards for domestic use. And with a
GSM phone, the
SIM determines the network on which the phone will work. With no VZW
SIM (for domestic use) a G1 + VZW = pointless.