Good question, one I've been asked many times before.
First of all, Pinterest is one of the fastest growing social media sites, now ranked third behind Facebook and Twitter. It began as a place to "pin" original art with quality imagery, graphics or photography. Now large corporations, small business and freelancers are using it to showcase their products and services.
Google occasionally publishes some of the updates to their algorithms through their blog sites. Typically they give some insight into how to modify your website to leverage the changes - or prevent a negative impact.
Here are some of the most recent:
Snippets with more page content and less header/menu content: This change helps us choose more relevant text to use in snippets. As we improve our understanding of web page structure, we are now more likely to pick text from the actual page content, and less likely to use text that is part of a header or menu.