ive had a pc in my own bedroom with a broadband connection since the age of about 14 or 15 and have had private access to the internet without any kind of supervision from the age of about 11.
Monitoring your kids conversations is just plain wrong - you wouldn't go along when they were with a group of friends and listen to every word they say would you?
Yeah there are some people on internet chat rooms that might say nasty stuff but hey - you CANT be hurt physically just by sitting at a computer, what you would be concerned about is if your kid wanted to meet an internet "buddy"
MSN is very safe, you can't talk to anyone you don't know/haven't accepted to talk to/haven't added and i use it everyday and have done for years.
Letting your kids meet people on the internet is a great - ive done it for ages, go to
www.faceparty.com and look for people your age etc and then get talking to them. Not every stranger on the internet is a 40 year old guy with no life... thats what everyone seems to think.
If you just ask your kids what they have been up to on the internet after they were online, and they get all twitchy about then you can perhaps assume something was up... but i would imaging everything would be hunky dory.
Of course you cant really get more specific unless the ages of the kids in question are divulged, but i'd say unsupervised access on the internet should be allowed from the age of about school year 7...
Thats my views,
Chris