I've done it. Several times. You've no doubt done it to, but you know as well as I do how often you narrowly escaped an accident while doing it. It's just so hard to put that phone down and not answer back. But to illustrate just how well (or poorly, actually) you do both activities at the same time there is an interactive driving and texting game at the New York Times that will test your performance.
Texting and driving is increasingly a hazard. Even when legislators ban it, people still do it. It is officially illegal to do in the Salt Lake City limits. But so is driving without a seat belt. Despite all the billboard awareness ads for both, there isn't much of a crackdown. BYU did a study a number of years ago that showed texting while driving is often more dangerous than driving drunk even. Would it be so hard to tell your friend "Hang on, I'm about to drive. I'll text you later" or if they text you right then while you are driving to either pull over or wait until you've arrived at your destination?