There's an interesting aside in "Made to Stick: Why Some Ideas Survive and Others Die" about feature creep. The authors parody the design of a typical TV remote: one designer wants to add a button that allows users to toggle between the Gregorian and Julian calendars, a feature that few users would actually want. But because no other designers are willing to put up much of a fight, the button gets incorporated into the final design. Before long, however, the remote is so overdesigned that it becomes difficult to do the basic things it was intended for: namely, changing the channels and adjusting the volume.
The iPhone, and phones like it, could easily have fallen victim to this desire to add features. Yet Apple locked itself in to simple by shipping devices with only two buttons and volume controls. Additionally, the number of apps that come with the phone are minimal, but users can download whatever additional apps they'd like. That way, users can have a versatile device without being bogged down by the niche features they don't want.
For instance, I love my MLB At-Bat, Kindle for iPhone, and RSS reader apps, but many people would see them as a waste of space. It's like we all have our own customized remotes now. One man's calendar toggler is another man's essential feature.