Social Media is a highly searched platforms, There are about millions of people who are daily active on those social media platforms. Many people use, many people are addicts to it, many businesses run on these Social media marketing platforms. millions write about it, their experiences regarding their marketing strategies, their user experience, their case studies.
If they write blogs or share their thoughts on high profile sites they get the do-follow links
Above mentioned words are just based on my thoughts, it may be just a coincidence if they relate with reality
;-)