22% of web pages contain Facebook URLs

"Based on a study of ~1.3 billion URLs crawled by Common Crawl in 2012:
22% of Web pages contain Facebook URLs
8% of Web pages implement Open Graph tags
Among ~500m hardcoded links to Facebook, only 3.5 million are unique
These are primarily for simple social integrations"

Source:  Zyxt Labs, 10th July 2012