Creating a GMail account now requires you provide a phone number to Google. A text message is sent to the phone number to confirm the account sign up.
The phone number requirement means GMail is only accessible to those with a unique phone number, plus it enables Google to link your activity to other on and offline records using the phone number as the database key. Once they have your phone number, Google can use it to correlate Google’s collected records about you with records collected by others.
When you sign up for a store “loyalty” card that allegedly gives you discounts, the primary purpose of the loyalty card is to get your name, address and phone number for marketing purposes. Stores use the phone number as a data base key to create a record of all of your store purchases. These records are sold to third parties such as Acxiom, which build profiles of everyone in the world. These databases are then re-sold to marketing organizations who wish to target specific consumers.
Just an FYI on that. Also, Yahoo Mail is doing the same thing now. This also means that is no longer possible to have an anonymous email account. Anonymous email accounts have been used by, for example, camera and technology web sites that collect industry tips or rumors from readers.