Come to think of it, this kind of behaviour may even act as a solid social filter. After all, if you cannot comprehend that I'm actually being an active part of conversation, notwithstanding my relationship with gadgets around, I'm not sure I want to continue conversing with you in particular.
Someone might call me on basic etiquette, but those are rules that are to be redefined at some point.
All the normal methods of figuring out that someone is actively engaged are broken when you introduce devices. Eye contact, physical gestures, mini-facial expressions etc don't work anymore. How is one to tell that you're involved? Random interruptions?
It's perfectly ok for someone to 'drop out' of the flow momentarily to check their little screen but they shouldn't pretend that they're still involved in the actual conversation.
Why do you think Google likes meta content? Because that defines context. And content without context is often meaningless.