Beenbeta- think you are getting a bit of needless abuse here!
I grew up in a lovely, warm, friendly home that I still count as home even though I haven't lived there in 13 years. We had lots of cousins and neighbours and no-one (in anyone' house!)would even think of going into the sitting room/lounge/whatever you call it (different thread in chat once, I believe). That was for adults, there were no toys in there, it was boring anyway
.
I don't think any of my friends have ever been in my parents' bedroom, or vice versa.
But there was no LAW, IYSWIM. I never felt I couldn't go into my parents' room (in fact I disturbed their sleep for anout 10 years
), but it was just accepted that there was no need for us to be in there to play.
However, I think a lot of this was because we (and lots of neighbours, etc) had a big house. Kitchen, 'den', playroom and a big garden - all our crap was in there and we had our drawings stuck everywhere, etc.
I don't think there is anything wrong with teaching children that the nice things in the 'good' room are there to be enjoyed in a different way, and that if my parents' friends came round, there was instant adult space. So no-one cared that we were building forts out of doll house and transformers at the other side of the house 
Sorry, loooong! Just didn't like the view that you were some kind of robo-parent, beenbeta!