Thanks for your comments. Let me address them:
1. As mentioned, every professional can see right away how it can be abused. We also did and closed all holes. The provider will able to block (or limit) any network connections outside the publisher's box (we might block it by default to avoid such concerns). Providers may block data persistence as well. They will also be able to work with specific trusted publishers (such as a University). That's where the beauty lies - it's an open and free market. It's all up to participant's decisions and preferences, including the pricing.
As for security on the provider's PC itself, it all runs in a restricted VM and the publisher does not gain elevated access even inside the Docker box, not to mention elevated or non-elevated access to the VM containing the boxes, not to mention access to the OS running the VM.
2. Right, Bitcoins won't be efficiently mineable over Xennet (unless someone gives access to his ASIC miner to the publisher, but why would one do that?). CPU/GPU mining algorithms based cryptocurrencies, though, will be mineable using Xennet. But still: it has nothing to do with justifying the existence of Xennet or the value of XenCoins. There are enough entities worldwide that desperately need massive computation power, and will pay more than crypto mining (AWS itself is order of magnitudes more expensive).
3. Xennet's main goal is not to save electricity. It's only a side effect. The main goal is to spread the fortune among the households, each contributing a small computational power, while letting anyone rent those powers. Recall that nowadays, households cannot really monetize their hardware, and most of the researchers does not have access to supercomputers, F@H etc.
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