Currently in the U.S. and across the world the iPhone is a GSM network only device. That means that even unlocked you can not run the iPhone on the Verizon network which is CDMA. This may change soon -- as early as Macworld 2009. Where does this come from? A Verizon tipster told 9to5mac that "Apple will be announcing iPhones for Verizon Wireless in 2009, perhaps as early Macworld 2009."
While there are many reasons that this rumor could be true we think these are the big ones:
Apple has been looking for EVDO and CDMA engineers with their job listings. You can check out these job listings