Actually, the risk of gas-station explosion from cell phones is another widely reported myth. Motorola commissioned an independent report a while back that concluded a properly operating cell phone does not contain a probable ignition source and a cell phone at a gas station is unlikely to be exposed to a flammable fuel-air mixture.

An IEEE safety committe also published an analysis (Apr 2004 IEEE Spectrum) of the energy needed to ignite a fuel-air mixture and the energy of potential sparks in a (properly functioning) cell phone and concluded there was not enough energy to make a spark big enough to start such a fire. The original is only available to subscribers, but here's a link to a reposting of the text.

Part of the reason this myth is widely believed is that there is a much more substantial risk of electrostatic discharge starting a fire at a gas station, and there is an industry awareness campaign to reduce that risk. It is easy to mistakenly associate the anti-static campaign with an anti-cellphone campaign.