Interesting. There was just a discussion on the Postgresql-GENERAL list wondering why MySQL is the default go-to database in OSS circles, and so much more popular. Nobody's quite sure why, though the fact that it's easier to run multi-tenanted (for hosting) came up.
Given the mention here of MySQL being a notably good choice to base Drupal on (because of it's popularity) I thought I'd ask for opinions here on why folks are using MySQL over Pg. I don't "MySQL vs Pg" comparisons; it's not about which is better so much about why you use one or the other, as both have technical strong and weak points.
Is this mostly historical, from the days when MySQL was fast but liked to eat your data (MyISAM) and PostgreSQL was just slooooooow and buggy? Neither of these things are true anymore, but if database choices were made then it'd influence long-term popularity and mind-share.