Prepaid Smartphone

While researching alternatives to paying exorbitant fees for smartphones, I came across an article that notes a method for doing this on a GSM carrier. To wit: obtain a sim card from a prepaid service like T-Mobile or AT&T, purchase an unlocked phone like the Nexus One, and go. The downside is not having a data plan, but most smartphones can use Wi-Fi for that. It's another option, anyway.