Something that contributes considerably to mitigation of the problem is to make changes "opt in". Users not opting in continue to get the old model. If you ju

Something that contributes considerably to mitigation of the problem is to make changes "opt in". Users not opting in continue to get the old model. If you just can't support the old model any more, the default is removal of presentation and/or removal of the information involved. A few people who can't be bothered to back up their own work and data, nor to respond to announcements of upcoming changes, may be pissed when items are "lost". But no one's privacy is compromised. Further, if you provide clear means of such a back up and/or instructions and advisement to maintain private copies, you can help lessen this second problem. That's something to Google's credit, that they've officially supported and developed means for users to retrieve their data locally into documented, usable formats.