I was ASTOUNDED to hear on this weeks Quirks and Quarks that only 30-50% of humans in the western world are methanogens ie methane producing. More precisely only 30-50% of humans have methanogens in their gut flora and have farts that contain methane. Gut flora refers to the microbes that exist in your lower digestive tract previously discussed on the bayblab of course. These methanogens aren't bacteria they are archaea.
From an old nature review "Faecal Matters":
Accumulation of H2 in the colon lowers the efficiency of microbial fermentation, while removal of H2 enhances microbial growth. There are three main groups of microorganisms that are responsible for H2 removal in the human gut — sulphate-reducing bacteria, acetogenic bacteria and archaeal methanogens. Around 30–50% of people in the Western world are methanogenic yet the human gut is thought to host just two species of methanogenic Archaea, Methanobrevibacter smithii and Methanosphaera stadtmanae.
Methane is the flamable stuff in farts that some dare devils have lit on fire using a lighter at just the right place and the right time. If you are unaware of the science of farts I highly recommend "Facts on Farts".
So unfortunately since only 30-50% of people of the western world have methanogenic archaea only these people can light their farts. This is really ashame as I'm sure there is no experience quite like it. (Caution: Facts on Farts warns of the dangers of 'lighting wind'). This calls for probiotics.