[Micah Lee on an Google security flaw he found](https://micahflee.com/2013/07/use-android-youre-probably-giving-google-all-your-wifi-passwords/):

> Go to your home screen, press the Menu button, select “Settings”, under “Personal” select “Backup and reset”. Is the “Back up my data” checkbox checked? If so, all of the wifi passwords that your phone remembers are being synced to your Google account.

… and those passwords are in plaintext. I haven’t changed my WiFi password in years, my passwords are changing today.