A common complaint among out-of-work Americans is they never really know why they were overlooked for a position. Their resume is solid, they're a perfect match for the job, but they don't land it.

John Moore, Getty Images

Chances are, these frustrated job-seekers may never get a good reason. Some employers shy away from sharing insight into their decisions, and they probably wouldn't remember every applicant anyway. With the proliferation of job sites like Monster.com, thousands of people can apply for the same position in just a couple of hours.

"To be blunt, you'd drive yourself nuts worrying, 'why wasn't I the best?'" said Chester Spell, an associate professor of management at Rutgers School of Business.

Spell said there are probably dozens of people who are a good fit for the job, but only one can be picked. At that point, he said, the "who you know" factor kicks in.

"The person they pick more often than not is somebody they know, or they know one of the references," said Spell. "Because that's all they can go on."

Networking remains key in this digital age. Spell's advice to job-seekers - get to know people in your field. Some hiring managers even host annual meetings or dinners that are open to the public.

"Computers, to my knowledge, are not making hiring decisions," Spell said. "It's still people."