From the developer's point of view, websites want basically two things: lots of readers, and easy maintenance.
Content Management Systems make websites easy to maintain -- by storing structured data separately from generated markup.
Microdata makes websites easy to find -- by performing roughly the complement of the CMS' job, i.e., by putting structure back into markup.
With Google, Yahoo, and Bing's announcement of schema.org, microdata is quickly gaining ground as a way to create applications that rely on data from many different websites. In this article, learn how to use Drupal to add microdata to your pages. Easily make your content available for use in applications such as Google's Rich Snippets.
The article doesn't worry about schema.org's close ties to the three big search engines (though it does drily name them a 'triumvirate'), because its approach is very practical: since, in fact, most people use Google (plus Bing and Yahoo), make your CMS generate sites that Google (and Bing and Yahoo) can find. Here's how they explain the present situation:
Schema.org is a vocabulary that works well with microdata. Because no approval body is in charge of vocabularies, the search engine owners were able to devise their own vocabulary to meet their needs. Most of the vocabulary deals with the kinds of things Google already focused on for its Rich Snippets: people, places, events, entertainment, and commerce.
Drupal 7 includes a module for microdata, so why not use it? (Drupal doesn't support it yet, but it seems to work straightforwardly enough.)
The DeveloperWorks article includes a large dump of excellent links to related resources, many of which are worth saving for review even after you've finished setting up Drupal's microdata functionality. So read it, and lead more people to your site with just a few clicks more.