However, I'm confused about how Google incorporates these signals. The majority of facebook pages are private, so if someone "likes" your site or links directly to your site, then Google can't crawl it. So this shouldn't add SEO value.
On the other hand, Facebook business pages are public. On my site's home page I have the facebook "like" button which links to my Facebook business page. Does the Google crawler actually notice or care when someone clicks on the "like" button? Are 1,000 likes better than 100?
For Twitter links, my understanding is that 1) they are nofollow and 2) Google doesn't even crawl them. So these don't add SEO value.
Sorry for the long post - I'm just trying to understand how to incorporate these different social signals into my backlinking strategy.