biggest fear is a greenhorn attempting to service a tire with oxygen, rarely completes the task without first starting a fire.
Left hand threads on the O2 hose unions help. I've still seen it done though.
In the past I had heard of allowable use of compressed air for a leg or two if nitrogen was not available to get it home to a station where nitrogen was available.
I think it is still allowable. AMM ref required though.
Someone once told me that N2 molecules are bigger than the gaps between the rubber molecules therefore they hold the pressure better. Not sure if that is just an urban myth.