Regarding mesh networking, you don't have to have encryption to do that. It could still be very interesting, you just have to know that people can inspect your transmissions. If they didn't allow this restriction, I imagine the system would just be overrun.
I think it would be very popular even with just a clear text internet over ham radio. You would probably even need additional restrictions to keep it from being overrun - like maybe only dedicated "ham radio internet" web sites would be allowed, as opposed to being just access to the (standard) internet.