Why does lighting a match after going number 2 make the stink go away?
 I've heard that the match preferentially burns methane, the carrier
of the stink.  Is methane heavier than air?  Should you keep the lit
match near the toilet or move it around the room?

Hello Nagmo,

Burning methane is certainly one of the possibilities, but the most
likely cause of smell removal is the sulfur effect.

For example:
  http://www.fca.com/articles/QC1.html
describes the effect as "camoflage"

  http://www.goaskalice.columbia.edu/2417.html
Go Ask Alice! at Columbia University indicates it is the sulfur smell
that covers up the other ones. Ventilation and air freshener are other
suggestions for removing that smell.

  http://frugalliving.about.com/cs/cleaning/a/090401.htm
Frugal Living at about.com also points out the sulfur effect; if you
want it to smell good, use "good smells".

  http://www.madsci.org/posts/archives/apr99/923460606.Ch.r.html
the "Mad Sci" Library message that goes into four basic scientific
explanations. #1 (most likely) is basically a placebo effect and #2 is
the sulfur smell. Combustion or absorbtion are #3 and #4.

Search phrases:
  bathroom match smells
  bathroom match combustion
  bathroom match methane

Do not hesitate to ask for clarification if some part of the answer is
unclear or you need a more extensive response on some part of the
answer.

  --Maniac

Of course I like to think that the match preferentially burns methane
and the stink, but I like the idea that sulfur dioxide covers the
smell!