A professor of business surveyed more than 9,000 managers and workers and found a familiar paradox: nearly everyone considers email checking and texting during face-to-face meetings rude, but most people still do it
But, it’s of course only rude to the person holding the meeting (and others who are "in charge"). ShakespeareGeek in the Lifehacker comments had this to say about the Double Standard:
Grab a manager and say, "Can I show you a quick something at my computer?" If you can get him to go over to your cube at all, rest assured that he’ll be checking his Blackberry while you try to explain your demo. Remember, it’s only rude if *you* do it on *his* time.