How serious is Social media marketing to search engines?

I read somewhere SEO used to be all about article directory submission.

Then, article posting.

The forum posting. 

Now the new kid on the block: SOCIAL MEDIA 

Do you see we are moving towards sites where more and more people are gathered?

Knowing that, i went back and revised my OMIM strategy again. 

Calling Online Marketing/Internet Marketing affectionately as OMIM.