The definition that I work with is: A smartphone has enough horsepower to run a general-purpose operating system (iOS, Android, webOS, etc.). There is an expec

The definition that I work with is: A smartphone has enough horsepower to run a general-purpose operating system (iOS, Android, webOS, etc.). There is an expectation that apps targeting this OS will be portable across most or all devices running the targeted OS. Typically, third-party developers have access to the platform. A feature phone only has enough memory to run custom-built firmware. There is no real expectation that applications will be portable across devices. Typically, the platform is only open to business partners of the manufacturer or carrier. To a certain extent Brew- and J2ME-capable phones trip up my definitions, as they are generally considered feature phones these days, but (in theory) you can write portable applications for them. They certainly feel like feature phones (developer access is very limited, and compatibility is iffy). For now I'll argue they meet my definition of a "feature phone" because you can only write any kind of portable application for them via a middleware layer. Anybody else want to throw in their two cents?