If you think Facebook and LinkedIn are somewhat interchangeable when it comes to furthering your career, think again.
While users can't decide if Facebook should be used for announcing what they're having for dinner (let me go ahead and offer a firm no on that one) or passive-aggressively insulting their in-laws, LinkedIn users are surprisingly loyal to the business interaction principle.
Facebook can be fun, don't get me wrong. But it can also be a little disconcerting when you write about your grueling work schedule and your boss responds with a smiley face. After foraging around in Facebook for any length of time, going to LinkedIn is like walking into a cocktail party with all the co-workers you like. You rarely see the LinkedIn premise misused. Sure, there's the occasional request for a recommendation from a former colleague you barely even remember, but for the most part, it's a helpful site.
When I get recommendations of "people you may know," it so happens that they are actually people I'm glad I know and would be interested in being formally connected to. With Facebook, 9 times out of 10 the friend suggestions make me want to seek a restraining order.LinkedIn lists job openings for me, offers suggestions for professional groups I might want to join, and even gives me a reading list. (See Figure A.) I love sites that do the thinking for me. On the other hand, Facebook offers me a mechanism by which to discern what breed of cat I would be.
If you're serious about your career, you should put your social networking efforts into LinkedIn.