Very useful and nifty if you
a) get locked out of your Google account or hacked
b) Google goes crazy and does even more nefarious things than usual with your so-called "private" data (privacy... how quaint).
c) you want Microsoft-formats of your stuff.
If you depend - as I do - on Google services, Takeout is a fabulous thing to know about. (They don't do a great job promoting it, of course).
Using Takeout to Backup your Google Files
- Log in to your Google account (just go to http://www.google.com/) and make sure you see your name / picture in the top right - or click on the blue LOGIN button on the top right.
- Go to Google Takeout by clicking on https://www.google.com/settings/takeout.
- Follow the instructions to select everything, or just certain things to "backup."