This means that the companies will not collect and maintain too much data about me to start with. There can be a reasonable amount of data - like name, DOB, address - that can stay public in any case. Other data will have to be deleted.
Any kind of personal data must stay privat unless I decide that can be revealed/public. Name, DOB, and address are personal data. I must have the right to prevent companies giving my address away (public or other companies).