Earlier this year, I asked a guy from IFI about setting the radio channel. He said you can do it with the little switches OR by using some serial-ish thingummy through the competition port. So, your code probably can't affect the channel unless it convinces a human to plug something into the competition port. The RC must still control its channel, though.
You might be able to do viral stuff by changing the team number and/or the backup battery behavior. Many people forget to reset their RCs after turning the robot off, letting it run on backup power. If you could change the firmware, you could have the RC use the radio while the robot is truned off. Then, you could scan channels and team numbers to establish contact with another robot.
Don't forget, this is entirely for your own entertainment. You'd better not actually use it at a competition (well, not at mine, at any rate

...)