I like Deb's analogy.... that being here is like being at a party. Some of us have known each other for several years, and some of us are new friends. It's much easier to 'mingle' here, and you don't need to worry about finding your purse at the end of the evening!!
It seems to be common for groups of friends to create subsidiary discussion sites that are 'private'. A group of us at a Border Collie discussion site created a private site, where we could feel 'out of the public's eye' and get into some intense in-depth discussions about training techniques. However, we still post messages at the public site and welcome new friends there.
Sometimes a discussion here will spark a desire to find another discussion site that specializes in a certain subject. I've found some new friends by joining some of those sites.
Oh.... and about being secluded from neighbors.... a few days ago, I posted on the "What Are You Wearing Today" thread, when I was at the office. After I posted, I walked over to get a cup of coffee and my boss said, "That sweater is an interesting color. How would you describe that?" OhMyGosh. My mouth fell open and I was thinking "what nickname would he be using in A2K?". He must have thought I was a total space case. It was just a random coincidence. (I think.)