Ed how are you going to ensure that this is safe? As we are always being reminded, this is a family site, so obviously there are young users and possibly children on here. I am very scared that they could be befriended by someone dodgy in private and give away personal details or worse! How are you gonna stop that happening? Especially due to concerns recently about users pretending to be young girls. It had been VERY obvious lately that people can register as many user names as they like so there is no way of establishing that the details they give about themselves are genuine.
While I do agree it is a parents responsibility to safeguard their children online I also believe that if a site is a family site which this is then the site should make at least a little effort to make sure the kids which may post there are safe whilst doing so.
Also a child may be silly enough to post their email address in public but if I saw an email address posted by someone we all knew was a kid then i would report the post and hopefully all the other adults on here would too to make it disappear. The thing with private message is the child doesnt need to post anything, the facility is there and anyone could send a child an uninvited message.