I keep all of the company registers and records, receipts, contracts, invoices, etc in Google Drive. We need to use Google Drive as it is the best of the options open to us for securely sharing files with accountants and lawyers.

I use https://github.com/Grive/grive to sync Google Drive to an encrypted local directory on my workstation at home. This is done daily.

Then I use TarSnap to backup that local directory.

Effectively I create an on-site copy of important docs from Google Drive, and then use TarSnap to create a secure and trusted off-site backup of those important docs.

Oh, and we also use TarSnap to backup our company (product) databases once a day too (though interim backups are stored closer to the servers too).

Our entire organisation is handled thus:

1) Systems and code via Github, and pulled often to one place (that local workstation) and then backed up.

2) Data dumps pulled locally and sent over to TarSnap of all product/customer data and all company files.

And the only on-faith thing is file attachments in the customer data:

3) Files via Amazon S3, trusting the durability of S3 and security of our interface to it.

This is all disaster recovery stuff. Secure, trusted backups.