From the blog:
If someone told you that there was a quick and easy way that many of you could improve your SERP CTR for minimal effort, you’d all stop in your tracks and give them full attention. Yet, Schema.org and rich snippets are still horribly under-utilized.
Since Google (and Bing!) officially introduced schema.org in June 2011, it’s fair to say motivation to implement it has been mixed. However since its introduction Schema.org has already evolved a lot, adding a lot of new stuff that people haven’t paid attention to. Here I try to persuade you there are few downsides and plenty of upsides.