...collected for specified, explicit and legitimate purposes and not further processed in a manner that is incompatible with those purposes;
...adequate, relevant and limited to what is necessary in relation to the purposes for which they are processed;
...kept in a form which permits identification of data subjects for no longer than is necessary for the purposes for which the personal data are processed;
In the EU, Schneier's proposal isn't just a good idea - it's the law.
Personal data shall be:
...collected for specified, explicit and legitimate purposes and not further processed in a manner that is incompatible with those purposes;
...adequate, relevant and limited to what is necessary in relation to the purposes for which they are processed;
...kept in a form which permits identification of data subjects for no longer than is necessary for the purposes for which the personal data are processed;
In the EU, Schneier's proposal isn't just a good idea - it's the law.
https://gdpr-info.eu/art-5-gdpr/