My code syncs to Dropbox. All of my projects (even experiments) are committed to private Github repos. I have two machines, so Dropbox essentially creates a physical backup on my secondary machine, which is nice.

I also have scheduled backups to an external drive, which enables file history as well.

So for me to lose my files, my main machine, my secondary machine, my external drive, Github, and Dropbox would all have to lose my data before I could get to the backups at any one of those locations (and all of them have incremental backups enabled, so I keep my entire history of changes).

Edit: Most of my clients and several of my organizations use Dropbox to send secret stuff, so Dropbox is already a single point-of-failure for my security. However, I am planning to move to something self-hosted and encrypted at some point. I'd love to put encrypted snapshots in Glacier from time to time and then have my main backups somewhere more accessible.