Today's featurephones have GPS, navigation, mail, IM, sometimes even installable apps. In 2006, we would have considered them smartphones.
If you read my original post, you will notice that I focus on the mobile broadband connection as the distinguishing feature of a smartphone. It is this feature that kept people locked into cellular contracts, raised the barriers to entry in the wireless world, ended Verizon's FiOS deployment, and ushered in the always-connected smartphone world that we live in today.
Technological realities are often more path-dependent than we like to pretend. Pay TV could be dominated by wired cable television (US), or broadcast satellite (Europe and Asia). We could've ended up in a Minitel world or an Internet world. A lot depends on business decisions and other non-tech dynamics.
In our case, it was the iPhone/AT&T combination that determined our path. That is why I used the definition that AT&T uses in exploring what it meant to live in a world without "smartphones." AT&T refuses to activate smartphones on its postpaid network without a data plan. Any phone that doesn't require a data plan is considered a featurephone.