How old should you be to get a cell phone

Ran across this atricle on the Detroit News' website about how young was too young to get a Cell Phone. It seems like in this tech-savvy world that we live in, complete with Social Networks and different apps, no one is too young. I see where a 9-13 year old might need one, especially if they are involved in numerous activities before/after school, and they need to call Mom and/or Dad at work to tell them that they made it home safely from sports practice or after-school tutoring, or if they need to stay at Music lessons or Dance class late. On the other hand, some of these kids, without parental controls installed, will call their friends at lunch hour or text message their friends in school. I remember my parents not letting me have one when I was a teenager, because, in their words, "You don't need one! Who are you going to call? You get one when you get a job to afford one". They finally caved in when I left home for college, and I absolutely needed one.  I think that the ideal age to get a cell phone is Fifteen, because that's about the age when some of these kids get really busy with school and other activities, and need to keep in touch with parents and friends. I've seen kid-friendly phones in the stores for the Tween set, displayed with the No-Contract/Pay-as-you-go phones. What do you think about this?