Recently , we got an example of why we need a read/write web. Some activities in life require to take certain risks while exposing yourself, and this requires that you can at any point go and edit or delete your data. Of course, the data could be massively harvested as soon as it is public, but there are two answers to that.
In a democracy, the law would be on your side. Look at how the music industry can take down data, and imagine if it could be at the service of the people. We could require by law that copying personal data that is already published elsewhere be illegal. This is not far from the GDPR.
Copies of linked data have inherently less value than links to the original data, because the copies could just be noise. Except, of course, if the data is signed. We don’t want signed data.