How does Google acquire personal data?
Google strongly urges you to create an account with them. Conceptually, that account is your online identity as well as a file. Every Google service you use will contribute bits and pieces of data to that file over time. You have little to no means to (really) delete that data. You might close your account, but some services (e.g. gmail) are designed to prevent you from doing that at the threat of data loss.
Furthermore, all Google services are tightly integrated into Android in a way that you actually have to make an effort into not using them.
An average Android user will provide Google with the following information about him/herself over time:
- A (unique) device ID and an account immediately upon powering up the Android device for the first time. The device id is uploaded along with the hardware configuration. Account and ID are suitable for further tracking, the hardware configuration is used for filtering apps on the play store.
- Search queries whenever Google Search or Now is used.
- His/her contacts through gmail and g+. Google also scans and evaluates all communications passed through it's servers.
- Real name and age when linking a credit card to the account for the purpose of buying goods on Play.
- Any profile information (gender, education,...) voluntarily entered into G+.
- Telephone number when using two factor authentication
- Current location when using Device manager.
- Non Google Accounts & Passwords (e.g. for connecting to WIFI networks) when using cloud backup.
- Personal preferences when syncing bookmarks and browser history.
The above list is by no means complete, but sufficient to get an idea that potentially everything you do on Android can get protocoled and most of it shouldn't.