Selected answers from the Dumb SEO Questions G+ community.
Chris Boggs: FurnitureStore, for example, would never "show up" as a little extra feature in the SERP. However, you may not need to fill out every field.
Neeraj Kumar: May not be relevant to the question, but some schema tags can be easily implemented with help of GTM. No need to make changes in codes. :)
Michael Stricker: Structure Data that feeds particular Google needs (e.g. Organization, logo, address to fit out Knowledge Graph) or Data that is voluminous but has recurring elements that Googlebot can then crawl and Index more rapidly, ignoring the repetitive page components (nav, footer) as an aid to full indexation and also to enable special SERP presentations like Instant Answers (recipes, prices, dimensions). The latter has earned criticism as Google chose to Index other firms’ Data and built their own presentations, for insurance, flights, hotels and more. That is a risk of making your data better structured.