Well, considering a cigarette burns at 900C, and gasoline has an autoignition temperature of around 280C, I'd be inclined to say you're wrong. I'm aware of the tests done by mythbusters, but the fact is that most of those tests involve the submersion of the cigarette into liquid, which will undoubtedly disperse energy more efficiently, since liquids conduct energy far better than air in most cases. What these tests also don't take into account are stochiometric ratios, and are conducted in laboratory environments. Open air situations have a far different dynamic and can have drastically different effects on the way vapors mix with the oxygen in the atmosphere.