One of the ironies of the Internet age and the subscription of the connected masses to Social Networking sites has been that surveys show that people want more privacy and increasingly understand the value of their information, while at the same time signing on to more social sites and sharing even more information in different formats like updates, audio, video, etc.
The reason is in plain sight. People like the features of Social Networking sites and what they offer, but simultaneously want their data to be private, protected and to retain control.
Here is an article and a video that are worth reading or viewing.
1- Ray Kurzweil, the director of engineering at Google, believes that his employer will soon know you even better than your spouse. By improving contextual understanding and interpreting the meanings behind what people are saying and doing on the Internet Google believes it will soon know you better than your life partner.
2- On a more light-hearted note, but certainly more immediate and no less sinister, here is a YouTube video that is food for thought.
And yes, Google will know, and remember, you watched it (perhaps it is better to skip it then).