Yes, you shouldn't text while driving, or talk on the cell phone, or argue with your dog or drive blindfolded. It's an idiot move, one that often leads to death (yours or someone else's).
I don't think you should text while working, either. Or use social networking software of any kind for that matter. And you probably shouldn't eat crunchy chips, either.
I don't think there's anything wrong with doing all that at work (in moderation). But not while you're working. Not if working is that the act that leads to the scarce output, the hard stuff, the creative uniqueness they actually pay you for.
You're competing against people in a state of flow, people who are truly committed, people who care deeply about the outcome. You can't merely wing it and expect to keep up with them. Setting aside all the safety valves and pleasant distractions is the first way to send yourself the message that you're playing for keeps. After all, if you sit for an hour and do exactly nothing, not one thing, you'll be ashamed of yourself. But if you waste that hour updating, pinging, being pinged and crunching, well, hey, at least you stayed in touch.
Raise the stakes.