[RickSanchez2600]

Google makes money off the activity and behavior of people using their free products. They sell the data to the highest bidder. If it wasn't free nobody would use them. This is to serve them advertising and sell info to spammers and marketers than will send them email.

[dastx]

Just a quick correction, Google doesn't sell your data. They sell targetted ads, that is, they promise advertisers that their ads will reach whoever they require targetting.