“The candidate with the most favorable Facebook profile picture received approximately 21% more positive responses to his application in comparison to the candidate with the least favorable profile picture. The difference in the chance to be immediately invited to a job interview even amounted to almost 40%. “

Source: Employers use Facebook (photos) to screen job candidates — ScienceDaily
Those who were judged more attractive were more likely to have their job application move to the next step. The researchers also did an experiment where they attached the photo to the application, and had similar results.
The main conclusion of their study is that employers do indeed look up applicants on Facebook, without the knowledge of the applicant. And those with higher attractiveness scores are more likely to progress through the hiring process.