While we have many different form factors of smartphones (many take the form of a “slate”, but we also have side-sliding keyboards, bottom-sliding keyboards, and candybar QWERTY), there's one form factor missing: the flip phone. In the history of smartphones, we've seen a modest number of flip phones. The newest one is the BlackBerry Style. Previous to that there was the BlackBerry Pearl Flip, and of course the HTC Star Trek (one of my favorite smartphones of all time). Flip phones are great because not only does the keyboard and screen stay protected when the phone is closed, but the flip is also functional: you can use it to answer and end calls, plus you can use the external display to see if you have a missed call, new email, or other notifications, without having to power on the main display.
The downsides to flip phones probably explains why we don't see them on the market: the screens must be smaller (and everyone wants a bigger screen, right?) and having a numeric keypad would seem a bit old-school (and BlackBerry probably has some serious intellectual property on a SureType-style keyboard in a flip phone like on the BlackBerry Pearl Flip).
But I beg to differ. I would LOVE a smartphone with a flip form factor with a number keypad, even if I had to contend with a smaller display. It would be more pocketable, and would feel like a true phone thanks to the simple dialing and easy way to answer and end calls. What about you? Would you buy a smartphone flip phone, or are you happy with available form factors on the market?