I don't like giving cell phones to kids younger than 12 or 13 because childhood should be free of a lot of the technology we use today.
The future is technology. You're holding them back, socially and technology skills wise, if you wait until they're 13 to give them a cell phone.
I was fixing computers and was generally the house technology expert well before I was 13. To get to that point required unrestricted access to tech and the internet. If I was locked down until 13, I would not be as successful as I am today in tech, if I was in tech at all.
Where in the world did you pull this out from?
As an adult, I'm proud of my technical accomplishments. But having no social anxiety, because I learned how to communicate face to face throughout my childhood, has been the biggest boon of all. Not joking.
[edit] I feel I should also add that not getting in to tech until already a teen has never felt like a deficit, or that I was starting behind anyone else. On the contrary, the non-virtual skills that came from playing with physical things like lincoln logs, tinkertoys, building models with friends, etc. gave me a intuition of how the world works that has helped me a great deal in getting my head around the nature of more virtual structures.