Take a look here this is a bit of the article
What if when you bought a new Macbook, the price was higher because your tweets constantly referenced your love and devotion for Apple? What if Orbitz used the fact that your Facebook Likes include “Party Rocking in Miami” to charge you more for a flight to Miami?
This is called online behavioral pricing. It’s a consumer’s worst nightmare as it uses the traces of your online identity to maximize prices on the products and services you want most. It’s also an ecommerce merchant’s dream.
So Be careful what you wish for...