Your post seems to imply that being able to control another room's lights is the greatest security threat. It isn't: reading other room's settings is.

While it would be annoying to have the lights turn on in the middle of the night, it would only be that (annoying). On the other hand, being able to read the current state of another room's lights leaks information about human behavior. It would be pretty trivial to get a statistical profile of the rooms to determine which rooms have occupants that have either departed or are asleep. These rooms then become targets for theft, vandalism or worse.