If someone came to your door and said, show me all of your photos, tell me everything that you've been doing and everything about yourself, would you?
I know I wouldn't. I'd send the stranger on his way and close the front door quickly. Yet that is exactly what we are doing with the social networking websites. We are telling them everything about ourselves.
But who are they? They are strangers, private corporations who exist to make money (as all businesses do). Their business model is to make money from data. And they go much further than just my simple example above, its more like they come over to your house and photocopy all of your photos and information (simulating how some social networks, such as Facebook, do not ever delete your data even if you close your account).
I used to work for a company that made its entire revenue from selling data. Data is worth money, lots of money. I'm a little disturbed by how easily social networking websites have found it to trick us into surrendering private information to them.
Perhaps that is the real genius of the social networks; you wouldn't tell a stranger you had never met the same information you tell the web... but are happy to tell a faceless corporation the same things because your friends are.
Be careful people. Big business has its own interests at heart.