I was wondering just how popular a pronunciation or spelling must be before it makes it into the dictionary. Browsing Quinion's page this morning I found a sort-of answer:

If enough English speakers decide that some word or phrase has value, to the extent that those who encounter it are likely to need to consult the dictionary in search of its meaning, then it is put into new editions. (Emphasis mine)

Found at: http://www.quinion.com/words/articles/howdowords.htm

So that's the vaguely-defined threshold, in case anyone besides me was curious.