Verizon just took a step in the right direction with their plans to open up their wireless network to any device by the end of 2008.
In 2009 (or sooner, hopefully), you will be able to take any CDMA device and use it on Verizon's network. This means no SIM card phones. Sorry, AT&T and T-Mobile fans.
Hopefully this is just the beginning and the first step toward wireless networks similar to those provided to people in the UK and Japan.