I think another benefit of asking Facebook family and friends is that no one feels obligated. If someone is happy to do it, they will say they are happy to do it. If they don't want to do it then they don't have to comment back or can say they are busy. I don't really care if they are making up that they are busy or not, I would just rather have someone look after my kids because they want to (even though I would pay them), not because they feel obligated to.