I wouldn’t normally comment on this in writing, but I cannot believe that there exists even one person who seriously entertains the notion that the iPhone (or anything else for that matter) should fail because it is impossible to use while driving. As pointed out by John Gruber, Rob Enderle holds such an opinion, as does Ken Dulaney (also via DF). It is nothing short of a miracle that these people are still breathing, never mind holding down paid positions as business analysts/writers/whatever. If you’re driving a car, you should be driving a car, not fiddling with your phone’s tiny tiny little keys.
I assume the people that the above articles are addressing are likely to be business users, people with Blackberrys and the like, in which case your phone is definately too fiddly to be used while doing anything else at all. I was on a bus last week that nearly hit someone who was sat in the middle of a junction talking on their phone, seemingly oblivious to the world around them. Hopefully the iPhone will force people to focus on doing one thing at a time, rather than driving around on auto pilot while pretending they’re sat in their office.