There's nothing to stop you building services on top of Tarsnap. In fact, I've deliberately arranged things (e.g., the flexible and easily scripted tar interface, and CSV format downloads of usage data) to make it possible to do this.
If you want to build a service on top of Tarsnap, please let me know and I'll do my best to provide you with whatever interfaces you need.
If you want to build a service on top of Tarsnap, please let me know and I'll do my best to provide you with whatever interfaces you need.