As far as the seriousness of the problem, it is low to medium importance at this time, but will get rapidly worse as wireless technology prolifertes.

I lay this directly in the lap of the FCC (here in America, anuway.) Equipment can be designed to minimize susceptibility to interference, but since it is not something that can ber determined to be a problem in the electronics showroom, some sort of susceptibility rating should be mandated to be reported "on the box", if not a mandate requiring better resistance to interference.

The added component costs are trivial. Remember, it's not the fault of the transmitters, but the existing receivers.

Out of curiosity, I did a few searches for aftermarket interference-limiting devices and surprisingly I found very little. There should be RF-filtering audio adaptors, speaker filters with quick connectors, and the like. There are a few, but not in the mainstrean electonic supply, other than the snap-on ferrite chokes at Radio Shack, which are not terribly effective for this type on interference.

I really expect this to change, though, as the problem gets worse. Also, fiber optic interconnects for audio equipment are becoming more common, which are completely immune to RFI.

Footnote: Corporations play games with regulation, too. A few decades back. a major computer manufacturer in the UK introduced their education-oriented machine into the US. Their US competitors managed to get the govenment to specify strict noise output regulations on the imported product, but not the domestic competitor. The shielding required easily added $50 to the foreign product, which amounted to a hidden import duty. (This was before PCs were as universal)

Mostly, it seems to me, the FCC responds to corporation's needs rather than those of the users.