The original reason for banning cell phones at gas pumps was coz (very rarely) the phone signals screwed with the pump signals to the computers and the gas companies were worried about losing money (similar to phones screwing with airplane guidance systems). The remotley possible "this phone can ignite gasoline fumes" thing was only justification.
The other reason they state is the distraction factor of gassing up while talking on the phone, which is as likely as the distraction factor of talking on the phone while driving I guess.
Matt
