Tor, or the onion, is a proxy layer that shuttles incoming and outgoing data packets through a labyrinth of servers, so that it's original source or destination cannot be determined via eavesdropping on the packet.
Tahoe, a decentralized least-authority file system, provides a way to store files on the cloud without being able to piece the file back together by mere eavesdropping.
The result? It would be interesting to see if Dotcom follows this approach, or another approach, to bring anonymous file sharing to the market. But until then, this looks like a not-too-dumb thing to use.
Tahoe and Tor: Building Privacy on Strong Foundations
Many people want to build secure Internet services that protect their users against surveillance, or the illegal seizure of their data. When EFF is asked how to build these tools, our advice is: don’t start from scratch. Find a public, respected, project which provides the privacy-protecting quality you want in your own work, and find a way to implement your dream atop these existing contributions.