Social media influences search results in more ways than you probably realise. Google looks at links from social networks and factors them in to their ranking calculation that influences your search ranking. Google can only crawl what it sees however, so if a Facebook users page is private, Google won’t be able to crawl it for links. Twitter links are generally tagged no-follow which means that all these links are visible they won’t contribute to your search juice.
Making Twitter links crawlable
You can use a service like twylah.com that aggregates tweets and displays links that Google can crawl.
Google Ranked Twylah Links