Caveats
Note that Google's terms of use prohibit the use of their services by any automated means or any means other than through the interface provided by Google. These restrictions would make use of GmailFS a direct violation of the Service agreement. As a result, Google would be well within its right to disable accounts used for GmailFS at any time and without warning. Consequently, GmailFS should not be considered reliable for backup purposes.
Read more about this topic: Gmail FS