what exactly is Fidonet?
It's a set of computer protocols that allows bulletin board users to share BBS messages and e-mails between bulletin boards. Pre-Internet. Relied upon phone calls between bulletin boards.
The weakness is that, compared to what we have now, it is s--l--o--w. The strength is that it doesn't depend upon Internet connectivity, which could eventually be filtered. It depends upon phone connectivity. With laptop computers being powerful enough to host bulletin boards, one could conceivably take a laptop and physically go to a truck stop and make the connections needed to transfer e-mails and bulletin board messages. Thus, it theoretically can be made almost completely secure and anonymous.