Well-meaning laws (or: I'm not a libertarian, but...)

Yesterday, a law went into effect banning using cell phones and other "wireless communication devices" while driving.  Out of protest, I made a silly comment to my Twitter account claiming that I was driving as I was posting it.  (I actually just pressed one button on my phone as I was turning into my driveway, and typed the rest after I stopped my car... just so it would be "technically" true.)  To my surprise (because I didn't realize anyone actually reads my Twitter posts), a bunch of people threw a fit.  So, to anyone that was offended:  It was meant as a joke, but my opposition to this law is very real.