Web 2.0 is a way to social network with friends and you join the social network websites and there are quite few of them poping up everyday.
Its like word of mouth advertising where your friends will tell their friends and it will be a viral effect.
Yes they all inter connected if you look your own blog Lisa you have a share this link where all the web 2.0 websites are.
Your readers can share your blog with which ever web 2.0 website they are member of.
I did stumble your blog today and by doing it its in my friendfeed and facebook as well so what happens is that your blog in stumbleupon where I would have friends and so would friend feed and facebook.
same will happen when I tweet
if you click on my friendfeed url you will see your blog stumbled.