Teach your children how to become good digital citizens. They need to learn these healthy online habits. But make sure they have the tools, resources and supervision to handle it responsibly. It could also teach them how to avoid things on the internet like scams. And they can get involved in fun social activity's.
I've had my present Yahoo! Account since I was six and either my mum or my dad set it up together with me. In this day and age, much communications is done through email and there's no reason to deny a child's access to it. Too many teens these days don't even know the difference between BCC and CC.
I don't really feel the risks as great as long as some monitoring is present and the spam filter is working. It's not like the kid is going to Nigeria if his/her parents don't allow it.
Kids' judgements are sometimes underestimated. When I was eight or so, I got an email saying 'Do women care about p**** size! The answer is yes!' I could tell immediately that the guy was an idiot and deleted the email.
Children should be able to have emails. It allows them to have a responsibility. They can also use it for school. Many school sites require an email for sign-up. I remember, when I was about 11 or 12, I really wanted an email, but my parents said no. They said I was too vulnerable to the world for emails. Everyone else had one, so I thought, why can't I? I'm not making that mistake with my children!
Children should not have email simply because there is little to nothing that needs to be done for children via email. If an email account is made for children it should be parent managed; there's absolutely nothing children should be signing up for by themselves and thus going through a parent's email or an email attributed to the parent makes sense.