FB can actually be a good tool if used the right way. It could be a sort of a 'profile' that you keep for your benefit. You obviously don't want to post there every trip that you make to the bathroom like some do, but you can create quite a good 'mystery' image of yourself. You can e.g. select a good (one) sexy picture of yourself, you can somehow keep updating your life here and there (with major events, e.g. hinting that you are adventurous and interesting), you can upload picture where you appear sort of a 'bad ass' and so on. If the person (girl) knows you directly and see some addition to your personality that she had no clue about, it is just a plus for you.
The trick is to keep it limited, at minimum, avoid negativity and avoid common stupidity. There are people who spent hours every day on FB, showing everyone how great they are doing, how happy their life is - it is just obvious that they don't have any life. If you show up every 1-2 months, post something thoughtful or even touching and then disappear again... good enough...
You want to create the impression close to "wow, he's really an interesting guy" and not "OMG, who is this person? He is totally different than the one I know in real life!". I noticed that many times, the people who have their profile on FB are totally different than the same people in real life. Don't do that, be who you are, be authentic. If you are shy you are shy, don't post your picturers online that you are the centrum of attention in some wild party or surrounded by 10 naked girls...
I originally signed up just to keep with my closer friends in touch, and thanks to FB I was able to contact people I haven't seen for years. I also posted recently a pic of myself doing 'bad ass' things, and I was unintentionally getting quite a good responses, girls who I haven't seen for 1-4 years started to send me their numbers, inviting me to stop by when I'm around, and one even called me directly. Girls do love bad ass guys...
Also remember, girls do talk, they have lots of friends. She may be just your friend but she may introduce you to her girl friend by showing you your FB page. So don't be stupid, post only what you won't regret in the future...
Unfortunately you can also get some orbitals and even stalkers, which is no good. It is annoying, and I am not surprised at all if a girl freaks out when she recognizes a stalker... So, don't stalk people, not on FB and not in any other place either...