Continuing your analogy, cell phones are like supermarket barcode scanners: weak and clearly red. It does not really matter how many of them you cram into a roo

Continuing your analogy, cell phones are like supermarket barcode scanners: weak and clearly red. It does not really matter how many of them you cram into a room, you can still send morse code with a green laser. All devices have small daylight lamp attached to them, the power of which is rather strictly regulated (IEC-61000, if anyone is interested). If you cram a lot of them into a room, morse coding with that green laser becomes difficult. You could increase power/brightness of the laser and call the problem solved. But then try to measure brightness of your lighting fixtures - becomes quite difficult. So no, proliferation of cell phones is only a problem for cell phones (one of the reasons for migrations 2G -> 3G -> 4G). The real problem are other devices transmitting in cell phone spectra effectively DDoS'ing them.