The essence of a conspiracy charge requires an agreement between two parties to commit a crime.
http://fas.org/sgp/crs/misc/R41223.pdf
Running a TOR exit node almost certainly would not constitute an agreement under federal law.
Indeed, see the following jury instructions:
http://www3.ce9.uscourts.gov/jury-instructions/node/475
> On the other hand, one who has no knowledge of a conspiracy, but happens to act in a way which furthers some object or purpose of the conspiracy, does not thereby become a conspirator. Similarly, a person does not become a conspirator merely by associating with one or more persons who are conspirators, nor merely by knowing that a conspiracy exists.
There's your defense. An individual running a TOR exit node with the purpose of passing news to people behind the great firewall of China does not become a conspirator because an anonymous individual uses that node to commit wire fraud. They had no knowledge that a conspiracy was being committed - they may have furthered it (by simply running the node) but that is insufficient for a conspiracy charge.