Ah, Facebook (News - Alert). Never before have so many been able to say so much about so little. You can find out all sorts of information about a person from their profile, from pictures of food they ate to their opinions about political issues summed up in an image macro. Those innocent posts can also cost someone a job.

It’s become more and more common for employers to look at Facebook, Twitter (News - Alert) and other social networks while looking at a potential employee. As such, nearly one in 10 people between 16 and 34 have been rejected jobs because of their posts. If one’s profile picture involves worrying behavior, or if they post something inflammatory (or just plain stupid), an employer is less likely to hire them, no matter how they acted during the interview.

Yet at the same time, many people know this to be true, and simply don’t care. Many feel that a company that won’t accept them for who they are isn’t one worth working for, while others design their profiles for friends to see, not business professionals. Of course, there are also those who just don’t know.

Some, however, lose their jobs because of posts or tweets they make after getting hired. If your profile is set to Public, or you have anyone who works with you on your friends list, then don’t post angry rants about your job there; save it for the bar. Even if your profile is private, and none of your friends on Facebook are co-workers, there’s always the chance of it slipping to websites such as “Failbook.” This is the Internet, after all, and posts can go viral.

However, some employers are going too far when it comes to looking at profiles. Some have been asking workers, or even potential hires, for their passwords to their social media accounts. That in itself is an invasion of privacy, and is actually illegal in six states. Other states have laws protecting employees from being fired for their posts on social media, although that won’t always stop some people.

We all have bad days at work, or worse, bad jobs at some point in our lives. There’s a natural need to vent when one is feeling frustrated. But while social media may be a great way to reach people, don’t insult your job on it. The pictures you’re tagged in and the posts you make do reflect the type of person you are, and employers will see them, so it’s important to remain presentable. When you put “Employed at” on your profile, you then represent the company.

For me, at least, I make sure none of my posts contain material that could reflect poorly on myself, even though my profile is set to Private. If I ever work for someone who doesn’t like geeks like me going to comic conventions in costume while on vacation, though, then I might be in a bit of trouble.