13 is a good age to get a Facebook or Twitter account. These social websites are intended exclusively for users who are thirteen years of age or older. A 13-year-old is a grown-up and comprehends how to be safe on these websites and exploits the safety features.
13 is a good age, with parental supervision only. A 13 year old is not a grown-up. A 13-year-old does not understand the dangers of the Internet. Remember, most of the answers you get on Ask are from other 13 year olds.