For a nice explanation of how I feel about cell phones, check out this video pointing out the ways that they are used. (My objection is not centered on that, but it is certainly evidence of a problem.)
We've all been in situations when someone opts out of whatever's going on, especially if there's awkwardness, to make a phone call or text someone. I've certainly done it a few times only to kick myself afterward. But what this guy says about it is right on and definitely how I feel if someone texts or calls another while we're hanging out-- "Anything coming out of this device is more important than you." Often I think it's just out of ignorance or lack of reflection; they don't mean to be rude. But.
Along these same lines, I have a certain amount of respect and love for those people who I know will almost never answer their phone or get to responding to an email right away. These facts seem to be serious affronts to a lot of people who've bought into this availability thing--"You are available to me at any time"-- but because I know that's not true- nor should it be- I see the so-called lack of communication as a sign that they are really being present where they are. (Which incidentally means that when I'm with them, I, too, get their full attention.) Seems a much more human way to be.