In the black side facebook will make you addicted, as we know that there are many applications in facebook, such as games, chating or other. It will make you interested and like to open the facebook oftenly but forgot about what your real live outside of facebook, your time and anythings else and also you you will fell if facebook is better than do another things which is usefull for your live.
In the downside, facebook is the media that will help you to contact and interact each other, Knowing the newest information directly and faster, also you can get a new friends also and getting closer with him / her, however you also can use facebook as a things that can help you to dicrease your boring as well.
All in all, facebook is just like a sword which the function is based on you wether you want to use it for a good things or bad things and you are the one who will get the cosequences of yours.