The Sidekick succeeded because it showed consumers how cool technology could be, that they could personalize a chunk of plastic and chips to make it their own, and ushered in an era of mobile computing for the masses. Say what you will about how fast its rising star burnt out, but the Sidekick is an important element in the link between cell phone and smartphone, technology and style.
No other phone got me as excited as the release of the Sidekick 3. It may be surprising that it wasn't the iPhone. I remember seeing friends with the Sidekick 2 and being amazed. Seeing them chat with friends over AOL Instant Messenger with a cellphone blew my mind. Without knowing it at the time, I saw the future of communication and mobile computing.
So many of us wanted an iPhone before we knew we wanted one because we saw the future of connectivity in the Sidekick.