Motorola Droid
SHOCK
Verizon (and Sprint) use a technology called EVDO. The DO stands for Data Only. Not sure specifics over why this was chosen over EVDV (data voice) but I would suspect it came down to cost and how quickly it could be deployed.
Now, they do have a new technology out that allows data and Voice using EVDO, but I'm not sure if Verizon will implement it or not.
In two years a good chunk of the country should be covered by LTE, (4g) which will support Data/Voice transmission.