it does annoy me when people you are socialising with or talking to start to operate their smartphone at the same time as nodding along to you talking to them. Happens all to often too
I find myself doing this, but only with boring work colleagues that I don't really care about, not with friends. If I was talking to someone and they did the same, I'd know I am being not very interesting and change the subject.
I have a galaxy S3. Do I need it? Of course not. Do I like it and does it make my life a lot easier than the guy that doesn't have it? Yes!