If the iphone does come to Verizon, why would it be US only? Verizon has CDMA Worldphone Blackberry's that operate as CDMA in the US and it has a SIM for international coverage.
True, excepting the Droids, most of Verizon's recent smartphones have been dual mode CDMA+GSM, including models from Samsung, HTC and RIM.
Verizon also will unlock the GSM sides for overseas, and people have even hacked some of the phones onto ATT stateside. Since Apple hates unlocked phones, that Verizon service probably wouldn't be allowed if it was dual mode.
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As for all those opining that Verizon would have the same problems as ATT, it's not technically possible for that to happen:
1) Both 3G networks use a form of CDMA, and tower placement is critical. Verizon used CDMA for both 2G and 3G and is okay. ATT started with 2G GPRS and added WCDMA radios later to get 3G.
ATT has recently said that their placement is far less than ideal, which results in congestion and dropped users. That's why they will have to add over a thousand towers to correct things.
2) ATT had to share frequencies between both their old GSM network and their new UMTS-3G one... unlike in Europe, where the 2100 band was set aside for UMTS. This causes congestion and interference.
3) Verizon keeps data and voice on separate carriers. A data user overload cannot affect voice users. On ATT's 3G network, a data overload can and does cause dropped voice and data calls.
However, both carriers have the need to upgrade their backhaul. Too many data users causes slowdowns.