Well, I’m afraid to say that this answer is very simple. Currently microformats affect SEO the same way content on your website affects it. From a web crawlers perspective there is currently no distinguishing factor between a microformat and standard content on your website. Why is this? Well, microformats are composed of common XHTML attributes and tags of information that are used in a standardized way, therefore engines such as Google and Yahoo treat it as exactly that, standard information. Does this mean microformats are useless in search engine optimization? No, not at all, microformats may be undistinguishable by engines at the moment but they still provide valuable content for web crawlers to index. An hCard for example provides Google with useful data about yourself such as an email, phone number, address and photo, all of which will be indexed into the Google engine allowing people to find your webpage based on your personal information. Sure, it’s not an SEO breakthrough but content is content so if you can get this information indexed in the engine why not do it using a microformat method and help increase the awareness and availability of microformats as a whole.