One scheme for addressing the problem of bad actors in open end-to-end networks is to guard the private/club spaces with gateways, firewalls, etc. If the bad actors are dumb then you can use simple puzzles to keep them our. A sort of child proof lock approach.
Over at telepocolypse Martin is wishing he could get one for his home phone.
“”Hello, this is not a voicemail system. You still have a chance of speaking to the owner of the house. Firstly, please press 5 star hash 4 to indicate you are human. Thank you. Now please speak the name of the person with whom you wish to speak. Your entry will be compared with our database. I’m sorry, large pepperoni with extra mushrooms is not in our directory. Please try again later.””
Maybe Mr. Gates owns the patent that is keeping that from appearing in home answering machines.