Looks like this article was written a while ago. Some of the ideas and/or techniques described may now be obselete.
As the Web continues to grow and evolve, it’s becoming ever more important to develop and encourage a common markup vocabulary to clearly express data. Enter Schema.org –a collaboration between Google, Bing, Yandex, and Yahoo! The aim of Schema.org is to provide us with this vocabulary, so we can improve the way information is displayed in search results. An example might be a recipe with a star rating.
When information is highly structured and predictable, search engines can more easily organize and display it in creative ways.
Effect on ranking
It’s tough to say what impact Structured Data has on search ranking, but it’s generally a good idea to give search engines what they want – and lately that includes Structured Data. Common sense suggests this will lead to better ranking. But what’s more obvious is the effect it has on your search result ‘rich snippet’ (the information that appears beneath your title on search results). A richer rich snippet tends to lead to an increased click rate, which is probably much more valuable to you than ranking alone.
At DesignKarma we’re still experimenting with Structured Data on this site and client sites, and the results have been mixed. Nevertheless it does appear to be a useful tool moving forward, and a standard that will be around for quite some time.