You’ve probably heard about employers asking prospective hires for Facebook passwords. You may even Google applicants' names to see what they might be hiding. That may be easy, but it can also get you in a lot of trouble.

There's no question that the exploding use of social media has put a tremendous amount of interesting information in the public eye. Many people don't think twice about what they post to Facebook, Tumbler, Instagram, Pinterest, a blog, or even good ol' MySpace. We've all heard stories about applicants who lost out on jobs when a prospective employer discovered photos of them enjoying a beer bong at a fraternity party (or something less legal).

Because it's easy to access many of those sites from your desktop browser, many employers figure that it's perfectly okay to perform a search and see what they can dig up. They may find some great dirt -- but they’re just as likely to find themselves on the wrong side of a legal action.

Here's why. Employers understand that there are certain things they can and cannot ask when developing an employment application or conducting an interview. Typically, that includes information about matters such as an applicant’s race, his or her marital status, and the like. The government and the courts have decided that such information is protected, and employers are generally prohibited from using it as part of a decision about employment.

If you look at someone's Facebook or Instagram site for just one minute, you can learn a lot about that person. What color their skin is, what type of relationships they have with other people, what they do on their own time -- all sorts of things that you as an employer are not supposed to ask about.

There's another issue, too. How do you verify that the John Smith whose Facebook page you're viewing is the same John Smith who wants to work for you? His name may be on that offensive blog post, but do you have proof that he actually wrote and posted it? What if someone who disliked him had posted it under his name?

In addition, there is some presumption of privacy with many of these sites. For example, Facebook users assume that someone who hasn’t been “friended” can't see potentially sensitive personal information. There have been some lawsuits against companies that have tracked down social media information without such consent.

But the biggest danger in performing background screening through social media is what you won't find. Suppose you screen all those sites and see nothing disturbing or incriminating. Is it safe to assume that the individual is squeaky-clean? Criminals, predators, and others who don’t play by the rules are often smart enough not to publish anything under their own names. They may have an entirely innocuous Facebook page under their name for public consumption, but what they may not want to share appears on another page under an assumed name. If teenagers are smart enough to post things that their parents can’t detect, wrongdoers are absolute experts.

Professional background screening companies tend to shy away from searching through social media sites for these and other reasons. Professionals understand the limits of consumer protection laws and recognize that using social media as a screening tool is inherently unreliable, and that it creates liabilities and other problems that exceed the value of the information.

The issue is a litigator's dream, and we can expect to see many high-profile court cases in coming years. Congress has also been considering legislation that would make it illegal for employers to ask for password information. With all the attention currently being focused on personal privacy, this issue is sure to get plenty of traction.

If you’re going to insist on using social media for background screening, be smart about it. First, don’t do it yourself. Let an outside firm go through the information first to screen out anything that should be invisible under the law. That might limit what you see, but it will keep you out of legal trouble.

Finally, apply common sense to what you do find. Young people may make poor decisions, and today, they can’t wait to share them online. But should bad behavior at one college party block an applicant several years later when he or she has presumably matured? Use your judgment and perspective -- and not just raw data -- to make those important decisions.