I do have a smartphone, but make a point of not using it when I have friends over. Mostly, they do not reciprocate however. If you actually take the time to observe the behaviour, it's actually quite fascinating, and yes, quite rude. More often than not, it's an obsession with checking social media sites, or posting to them. I felt I was slipping into this trap, and mainly for that reason, I've disabled my Facebook account. I haven't even logged in since February, and you know what, I don't miss it in the slightest - and it actually feels empowering and freeing.