The crypto in Tor makes it CPU-bound. From the discussions I've seen, top of the line relays max out around 300-400 Mbit. That is why the Torservers are carrying around 30 MB (240 Mbit). 1. Because their theoretical maximum is so low. 2. Because few relays carry their theoretical maximum, even the exit nodes. I believe herngaard was pushing 50 MB at one time, which is 400 Mbit, and that's the most I've ever seen. So having a 1 gigabit port doesn't mean much. In order to push 1 GB, you will need 30+ servers.