So, it's funny this thread came up today because I was just thinking about HAM radio applications for bitcoin. Transactions over the radio wouldn't be super-feasible using voice modes (but perhaps using digital modes). They need not be encrypted, just signed. AFAIK, sending a cryptographically signed message for authentication should be fine since the data is in the clear. Here's an extensive write-up on the subject:
http://blog.rietta.com/2009/08/authentication-without-encryption-for.htmlWHAT DOES PART 97 SAY?
Section 97.113 (4) "...messages in codes or ciphers intended to obscure the meaning thereof, except as otherwise provided herein..."
Based on the above quote, we can use any method at our disposal to provide for secure authentication which does not obscure the meaning of communications.
HAMs could get a vanity bitcoin address with their callsign, and use that to receive donations (like for rare DX), sell products, contribute anonymously to radio clubs/nets, participate in contests where rewards are sent via bitcoin, etc. In fact, I'm generating one for my callsign right now (sold all my video cards, so it's SLOOWWWW - will take 2 hours).
If I manage to get my radio going (HF), I'll post in here, and if another HAM is interested I'd love to send some µBTC to them after a radio negotiation. The HAM community is VERY technical, and has a sort of libertarian streak at times, so they should welcome BTC IMHO.