We all know the basics: when you sign up for a Google account you provide valuable personal information that allows hardworking people at the company to build a profile of you.
This will include your age, your interests, your contacts and much more. You trade your data for an easy ride on the internet.
Read more, very interesting...:
http://theconversation.edu.au/google-slapped-hard-in-europe-over-data-handling-10270