Joseph, my children (teens)do not require a facebook account.
We allowed them to have it because we are very involved parents who are able to monitor who our kids communicate with, for how long and what the conversations are generally about.
As far as the danger, there is danger is just about everything, including water, food, walking to school/shul. I don’t weigh out their foods, I don’t monitor so closely how much they dring during the day and I don’t check their bowel movements. Standing in line at the grocery store to look at magazine covers can also be seen as dangerous. My job as a responsible involved parent is to educate my children as to what is appropriate and what is not. Thus comes the act of communicating with my kids. This teaches them to make good / appropriate choices. What to do while standing in line at the store instead of gauking at the mag. covers – what to say and who to say it to on facebook, its all about helping our kids “do the right things” in different situations.