Android M weird shared preferences issue

Question

On my Nexus 5 running Android M Developer Preview 2, when uninstalling/reinstalling an app, the device is retrieving shared preferences I stored long ago, for instance a boo

Answer 1

That is because Android M will feature Automatic Backups (old link).

Extract:

The automatic backup feature preserves the data your app creates on a user device by uploading it to the user’s Google Drive account and encrypting it. There is no charge to you or the user for data storage and the saved data does not count towards the user's personal Drive quota. During the M Preview period, users can store up to 25MB per Android app.