According to a recent survey conducted by Michigan State University, 36% of companies now use social media for recruiting. In addition nearly 80% of adults 18 and older are online. See this graph, from the The Pew Internet and American Life Project, for an overview of Internet usage in the last decade.
Some interesting statistics:
If you work in higher education and want people to take notice of your work, department, or institution then consider promoting yourself through social media.