If you have an old-ish head unit in your car, it may receive an RDS (Radio Data System) feed that could tell you what station it is or what song is playing. However, many stations around here are using it to advertise Club Fitness and Golden Oak lending. If you cast further back into the mists of time, anyone could send you a webcam or chatroom invite ... this was naturally exploited by spammers approximately ten milliseconds after its invention.

I have since formulated the concept that any communications channel, any at all, where it does not cost to transmit per message will eventually be colonized by the advertising fungal organism. Even low-cost messaging can be colonized, but the lower the cost, the faster it comes.

Similarly, like FreeNet, any communications channel that can be used to post Things You Do Not Like will be used to do so. And that once you implement some kind of wide-scale filter against that, absolutely nothing can be done to stop someone from attempting to take over, to add and subtract to that filter, for their own purposes and their own ideology.

I have no solutions for this.