But then we get to Facebook, which started as a social network primarily for college students (in its early days only individuals who had an email address ending in ".edu" could join). Soon others were able to join and now all generations are using it. As Facebook grew in popularity, and individuals could also create Facebook "pages" for their professional endeavors, the line between personal and professional online presence quickly blurred.

Even though Facebook provides a variety of privacy settings which, in theory, protect users from revealing information to the wrong people, there are many ways things can go wrong. For one, the privacy system is somewhat Byzantine in design — it's not as simple as just limiting your posts to "friends" and assuming you are safe. After all, everyone is a "friend" in Facebook, so you need to further refine categories of people. This means creating special subgroups (for instance "professional contacts" or "close friends") and then making sure that when you post, you specify which group will receive that post. And even if you control your own posts, and limit controversy (politics, religion, what bar you were in last night, etc.) you still have those pesky "friends" who might tag you in photos or post something controversial on your wall. Furthermore your friends might have settings much more public than yours, potentially exposing your posts to a wider audience than intended. Finally, depending on your settings, friends can download your photos the minute you post them, so even if you remove that less-than-flattering photo later, they may have already captured it.

Many of these factors can be controlled, of course, but at some point Facebook loses its appeal: if you're spending more time strategizing and checking your privacy settings than enjoying Facebook it might be time to rethink how you're using it.

So, keep it simple, right? Just don't accept any professional contacts as friends. Or, if you do, monitor your privacy settings so those professional contacts don't get your personal posts. But that's not what people generally do. Just read the latest report from Dan Schawbel, a leader in the branding industry — particularly as it applies to individuals in Generation Y (ages 18-29). I spoke with Dan recently regarding a study his company, Millennial Branding, completed on the Facebook behavior and attributes of Gen Y's, particularly in relation to career development activity. What he discovered was interesting-- and in some cases unexpected. (Here is a link to the complete report.) Here are some of his findings:

• 82% of Gen Y's have a least 1 Facebook friend who is also a work colleague.
• 53% have more than 5 Facebook friends who are also work colleagues.
• 40% have more than 10 Facebook friends who are also work colleagues.
• In addition, while 80% of GenY's list at least one school on their profiles, only 36% list a job or employer, perhaps indicating that they are not viewing Facebook as a professional networking site.

This blurring of personal and professional life online can provide a cautionary tale for job seekers. As Dan points out, the Facebook "friend" today could become a "coworker" tomorrow — meaning they will have had access to your pictures, posts, etc. "Gen-Y needs to be aware that what they publish online can come back to haunt them in the workplace, he says. "Gen-Y managers and co-workers have insight into their social lives, which could create an awkward workplace setting or even result in a termination." They might even be your future boss — or someone who has the power to hire you.

(If you'd like to see a snapshot of some of the information from the study, here's an interesting infographic. When you click on this link, the infographic will be rather small; simply click on the infographic itself and it will open in a larger format.)

An article in Forbes points out even more dangers of Facebook profiles coming back to haunt job-seekers, with items they've "liked" creating controversy.

Bottom line: Even in a well-protected Facebook profile, avoid posting anything which could threaten your current or future employment. You really don't know who might be looking.

I admit that this is an ongoing challenge for me because I have friends within my profession. I deal with this by keeping it simple. I have a professional Facebook page exclusively to repost blog postings, answer questions from those who have "liked" my page, and otherwise connect with potential readers. I post nothing personal on that site.

I set my security settings on my personal profile as tight as I can (limiting almost everything to friends only) and then I'm careful about what I post (and what I "like"), knowing that my control of the information is limited. I'm guessing the greatest career damage I could incur would be boring my professional friends with my musical tastes — my primary hobby is playing guitar, banjo and hammered dulcimer, and many of my Facebook friends are fellow musicians and music-lovers so my professional friends are regularly "treated" to posts of YouTube videos of (generally obscure) songs I enjoy or am trying to learn. Come to think of it, maybe all those banjo postings have impeded my career...

Just be smart. Know that what you post online is seldom, if ever, truly private.  And a friend today can be a coworker tomorrow who now knows all about you.

©2012 Katharine Brooks. All rights reserved. Find me on Facebook and Twitter.

Photo credit: StoneySteiner