Gabrielle Roth gave a very funny presentation at PgCon this year, about what she called "the world's most unpronounceable database". You might be curious why our community has so many different spellings and pronounciations.
First, 'postgres' is used by many of our community's core contributors. The original project that eventually became PostgeSQL was in fact named "POSTGRES", a pun on Ingres. Later, when support for SQL was added, the community tacked the SQL on, created a logo that emphasized the SQL, and eliminated an 's' critical for pronunciation. So now, we regularly hear people from all over the world saying 'post-gray' or 'post-gree'.
This conference's bias is obvious. We like using 'postgres' because it seems to help the most people feel confident that they are saying the word as others would say it. 'Postgres' is also an accepted alias of the project.
We still love hearing the variety of other interpretations, but we'd like those sharing our name to feel confident in stating it out loud.