In a completely unscientific review of community popularity I was reviewing the active members of various channels on #freenode. For those that don't know, Freenode is the defacto destination for the Open Source community on IRC. This is where you will find official community support channels for such open source luminaries as #gentoo, #ubuntu, #mysql and of course #postgresql.
The List
Ubuntu
Gentoo
Linux
Debian
Python
ArchLinux
Django
Haskell
Perl
C
Git
RubyOnRails
C++
PHP
Fedora
Jquery
Vim
KDE
PostgreSQL
Drupal
I find a couple of data points that can be made from this list. Debian and its kissing cousin Ubuntu are clearly stomping everyone around them in the community driven Distro wars. There are surprising entries such as ArchLinux, Haskell and Vim. O.k. I am not surprised about Vim, if you are using it you clearly will need a lot of help.
Even as a Python zealot I was surprised to see that it was above Perl in the listing. However to be fair I know that there is an irc.perl.org which has a large base. There is not an equivelant for Python so it is quite possible that if you take into account irc.perl.org, Perl would overtake Python.
Of course all of this is dodging the real point. The real point is that the "World's most popular database" isn't even in the top 30. Now there will be many out there that say, "You can't judge the community by IRC alone." That is certainly true and I am not trying to spread doom and gloom about MySQL. The only reason I am pointing this out is that it was just an extremely short while ago that MySQL consistly had more users in channel than PostgreSQL.
Power to the Elephant. Power to the People. Fight the Power.