The participating entry-nodes (proxies?) could be systematically determined with a scanner
How, exactly? Measuring the run-time of packets and comparing to the expected run-time? I suspect this could be masked by the proxy, but I'm not sure.
You have to trust the people running the entry nodes
You can encrypt the payload independently and then re-encrypt it for the HTTPS tunnel. But as with any proxy, they know the ultimate destination for your traffic, even if they can't get at the data itself.
How, exactly? Measuring the run-time of packets and comparing to the expected run-time? I suspect this could be masked by the proxy, but I'm not sure.
You have to trust the people running the entry nodes
You can encrypt the payload independently and then re-encrypt it for the HTTPS tunnel. But as with any proxy, they know the ultimate destination for your traffic, even if they can't get at the data itself.