As explained in the article about microdata and rich snippets, Joomla does not offer support for microdata in the core. If you want to enrich your content with microdata you need to creat or buy overrides, install extensions or activate the feature in your extensions, if applicable.
One of the main 15 new features of Joomla 3.2 was the support for microdata. For the time being though, this does not mean that microdata are actively used in Joomla. The added support is a new library for Joomla developers, which allows hem to easier create the feature in their extensions and plugins.This is achieved by adding the JMicrodata class. The improved support will hopefully mean that in the near future, microdata or rich snippets will actually be used on your sites.
An interesting article about this development by one of the developers (Alexandru Pruteanu) is also available on http://magazine.joomla.org, where the possible future use of the JMicrodata-class is explained, plus possible use of this, like possibly a switch in the Global Configuration screen, under the SEO-settings where you can possibly switch off or on this feature. On top of that, you should be able to further finegrain this in the Article Options, where you can also choose between different microformats, like Blogpost, Newsarticle, Recipe, etc.
For some more technical backgrounds, read this article.