Not neccesarily. It could cause some fierce reactions, but the low temperature of the atmosphere is going to limit the spread of any open flame by quickly robbing it of energy. I just looked it up, and Titan has an atmosphere 60% denser than the one on Earth. That dense atmosphere would also slow the spread of any flame, allowing the fire to burn out all of its own oxygen...it would effectively self-extinguish.
Of course, this assumes that the methane density is high enough to maintain a sustained burn anyway. I haven't found anything on the actual relative densities of the gasses sampled by the probe, so I'm not sure if there's even enough fuel there to ignite.
That's why they compare Titan to early earth: before free oxygen. First fix all the combustables out of the air, methane, etc., then start liberating oxygen. Do it the other way and you'll end up with a nice fireworks show and a burnt-out cinder.