Take my blog as an example. It's me talking with an audience of visitors - people like you. The visitors to my blog know my site, but they don't know each other - they are strangers in a community of the likeminded. I recently started looking at the locations around the world where my blog visitors visit from - see image below. It changes each month, but most months the densest concentrations are usually in London, New York, and cities in California. They are less than the legendary 6 degrees of separation away from each other, frequently living in the same city, but divided by a 'connection gap'. Only those that leave comments are recognized, but more people could be sharing and connecting if only they could connect.
Google Friend Connect is supposed to remedy this for people you already know. But surely in the future, we will have systems that connect people who have never set eyes upon each other, but have a common interest, or a shared goal. This I suspect will be an interesting consequence of the semantic web: connecting people as well as connecting knowledge. And when this is posisble, the saying 'there are no strangers, only friends you are yet to meet' takes on a new significance.