There are companies that aggregate your data from all over the place (online, shopping habits on your credit cards, what you buy, where you buy it and even what you own) and sell it to advertisers. This is why people don't like google and Facebook One of my clients is a company that does this. In a meeting earlier this year their president/CEO said "nobody knows who we are and we like it that way. We're the people behind the curtain. We are the creepy people that take all your data." Sleep tight.