If Facebook Cloned Gmail . . .
Inspired by Anil Dash:
If Facebook built Gmail, only you could see your Inbox.
Six months later, your friends could see your Inbox.
Six months later, friends of your friends could read your Inbox.
Six months later, the Internet could read your Inbox.
Because, although you don’t know it, you really want to share yourself with the world.
Of course, each time the defaults change, you would be able to reconfigure the defaults, but you would have to find the new and improved settings pages and learn how they work.