Per a news report I noticed today, it seems New Zealand's Electoral Enrollment Centre has "consolidated the country's electoral roll on the open source PostgreSQL database". Sounds like an interesting project, and a very good use for an Open Source database in general and PostgreSQL in particular.
It's not a particularly huge database, but it's distributed. And they're even running it on 7.4 (though they plan to upgrade) which certainly means they're missing out on a lot of things in 8.x, so they'll likely be even more pleased in the future.
And it's a matter of principle when it comes to sensitive data belonging to the public /mha/templates/default/img/emoticons/wink.png alt=";-)" style="display: inline; vertical-align: bottom;" class="emoticon" / Dealing with it using open source software just makes a lot of sense (even more than just the monetary savings and the very stable platform that you get). Now I just wish something similar would happen here...