Well, if you have a FHSS frequency hopper, you could jam on all the channels except the one you are talking on at that instant (for 50ms or however long you hop

Well, if you have a FHSS frequency hopper, you could jam on all the channels except the one you are talking on at that instant (for 50ms or however long you hop). That would make the spectrum unusable by anyone except you. (It's also why regulatory bodies have strict rules on how long (and short) you can idle on a channel, how you have to hop through all channels before transmitting a second time on one, etc...)