Doesn't work like that Rambler. The UDID of your device is stored on Cydia servers against your account. Even if you do a fresh restore of IOS and never provide your Google or FaceBook ID to Cydia on a clean install, if it recognises your UDID it will allow you to restore your previous purchases. Of course you cant buy anything else unless you log in, but you can install what you own without providing your details. It is a bit of a loophole which is balanced with the convenience factor for the many more people that will never sell on their devices...