Asinine. I am scratching my head wondering why our existing x-ray and explosives detection technology can't address this.

To me, it seems simple:
1) Either someone voluntarily hands a toner cartridge over or one is found via x-ray imaging.

2) Swab toner cartridge, unshrinkwrap if necessary, scan for explosives.

I really haven't seen many people use carry-on to transport toner cartridges--but if someone has a need to, I don't think this process would be onerous for the TSA.