What good social media does to your website's traffic and your organization's public visibility.
Here's the whole realm of possibilities of what social media can do and how it translate to search engine rankings, IF you're using it well. I don't have a ton to add here, but it's a good visual representation of the complexity and the potential of the internet. Things really have gotten a lot more complicated than just sending out a mass mailer and hoping for the best. Thankfully, they're also a lot more measurable.