constant distraction. The lulls in conversation are when the best ideas are allowed to flourish.
A recent article in Forbes includes social-media addition as Habit #9 of 14 habits that can get a person fired. This is a bit tricky, since mastery of social media is often important in finding a job and in advancing the goals of an organization. But it can very easily get out of hand, and interfere with the all-important matter of being present.