Facebook and Twitter Likes Do NOT Lead To Higher Page Ranking
"There are a lot of links on Facebook with a lot of likes and it ranks well. That's correlation , NOT causation." --Matt Cutts
Small businesses MUST use social media to help promote their brand. Your personas are using social media. This is the best place to interface with your personas and tell them about your brand. It is also a great place to learn about what they care about. But links and likes on social media does NOT mean that this site will rank in on Google.
Matt Cutts explains that Google is looking for quality content. It isn't necessarily using "signals" such as likes from social media to determine if content is high quality content and thus should be ranked higher than other content. The reason is simple. Social media is imperfect.
1) Google Bots are often blocked from crawling social media and content
2) A person "liking" content and linking to it doesn't mean they have been to the page and spent time on the page.
Let's face it...issuing a like on social media is really easy. Putting in searches in Google in order to find something isn't as simple. Keep this in mind when you see your content "going viral" on social media. It doesn't necessarily mean you climb the SERP.