Facebook is not a good place for any singles! Whatever you put on the Web stays there forever!
Just because they’re good kids does not mean they can’t be dragged into Shmutz!
My daughter was in shidduchim and it wasn’t going. And she had a Facebook account. My wife and I asked her to give it up until she got married. Two months after she gave it up, she got engaged. Now that she is married it is up to herself and her husband, just like everything else in life!