Same here, I left when I was 18, to go to uni. I'm actually still in touch - rather, facebook has renewed our contact (friendsreunited.co.uk was still a paying site back then!) - with some of my oldest schoolfriends. Only my cousin, who's over 20 years younger than me, is on fb and I have to say, I'm somewhat relieved about that!
I know what you mean about going back... it's fast coming up to five years since I last stepped foot in my original homeland and the thought of going back fills me with dread. One of my expat mates in Wellington went back a couple of years ago and couldn't wait to leave. Usual story - loved catching up with everyone, hated being there and felt so hemmed in with all the crowds.