If a person is seriously anal about their career, they can create a facebook account that is very professional with all sorts of professional “friends” and comments. Then, when potential employers scour around for information on you they will be duly impressed.
And if you have a facebook account they will almost CERTAINLY find it and review it. You can pretty much count on it.
Note, I work with an HR department as part of my job.
How are they going to see anything unless I add them as a friend?