LinkedIn, owned by Microsoft, hosts the profiles of nearly 800 million people in over 200 countries and 2.8 million locales -- and up to 47% of them are active users. LinkedIn reports 97 million monthly unique visitors worldwide, 57% of whom log on via mobile devices. In the U.S., 27% of adults (180+ million users) have LinkedIn profiles.

Over 30 million companies have company pages on LinkedIn. Furthermore, according to LinkedIn, there are executives from every Fortune 500 company using this social network, and 95% of those companies use LinkedIn's licensed recruiting software to search for job candidates.

LinkedIn is reportedly the most trusted social network in the U.S., with 73% of users agreeing that LinkedIn protects their privacy and data. That's way higher than Facebook at just 53%. This is good news for LinkedIn's job search audience of 40 million people per week.