Googling a name is a very simple procedure and it´s almost guaranteed that an employer will Google you name before he or she will interview you to let you say something good about yourself.
Employers want to make sure that they hire the best applicants out there. It has surely always been like that, but today there are some opportunities for the employer to investigate who they even want to interview.
So what does a simple search on Google say about you? Facebook has a lot of power and even though you haven´t been tagged on your friends party images in example, the employer could experience doubt about you just by the people you associate with.
A resume and a cover letter can take candidates very far by having a professional looking at it before sending it to a company, but a professional online presence is even more powerful because it shows that you are respected by your peers and previous teachers and managers.