Webcams themselves are great to have and I do sometimes use them to talk with friends or even my aunt and uncle (we use skype-skype computer calls so it's free and also use a webcam). However, my friends, family and myself are all old enough to know the possible dangers out there on the internet. I say if you let the 11-year old use the webcam, then have some sort of supervision over it, such as use it with you or let him use it but have a restricted internet access (although that wouldn't block everything harmful).

If I had a kid (which I don't, only 19 years old and in university), I'd let them use something like MSN or skype or similar things like those. They're free, you talk to whom you want and have very little harmful things on them.

If you do wish to let him use a webcam, then somehow make sure he doesn't start chatting with strangers or visiting inappropriate/harmful websites.