Creating and maintaining an online presence is an important part of your job search. Many people I speak with do not feel that it is necessary for them to have an online identity. However, it is not uncommon for potential employers to Google job applicants. Knowing this, it becomes more apparent why it is so important to have an online presence. When you are googled you want information that YOU want to appear to be there and wow your potential employer!
Creating an online presence does not mean you must suddenly join Facebook, Twitter and LinkedIn all at once! If you are just interested in a strictly professional presence then LinkedIn is where you should be focusing your attention. LinkedIn is like a Facebook for professionals and offers a great way for you to network and keep in contact with that network. Maintaining and creating relationships with people in your field of interest is integral to you being successful in your job search and LinkedIn acts as a tool to enhance these networks and relationships.
LinkedIn allows you to highlight important work experience and gives you an ability to control what pops up if your name is googled. Having a LinkedIn profille pop up in google is better than having nothing appear at all!
Read more about this topic from the Harvard Business Review article Managing Yourself: What's Your Personal Social Media Strategy?