I can't be separated from my smartphone. I'm always on Facebook and Skype and MSN and texting people and all that stuff. I'm essentially instantly contactable at any time, using the mediums of communication at which I am best.
It just makes sense to me. I do much better at text than voice, and with text-based communication I can communicate much more of the time versus voice, and because of this my phone is like another limb.
On top of that I use it as an alarm clock, calendar, thing to remind me, flashlight, camera, music player (and storage for now), making rough recordings of ideas so I don't forget them (musical and non musical), just all sorts of things aside from communication.