And what will happen when China raise the big firewall and block any bitcoin activity ?
Or when Goldman-Sachs-controlled Europe & US do the same? Once Bitcoin became a serious threat to them?
Tor?
Tor is for the casual user. If we are talking about mining farms, they can easily get out through any pipe really. SSH, VPN, whatever. The oppressor would have to block all encrypted data, but then again there is always the stego route. It would be much easier for them to find the farm physically.
Why would any agency waste that much effort for this kind of endeavor, I don't know. It's more likely that they would attack relay nodes.