Indeed. I was reading a tragic article about the energy cost of bitcoin and I started to wonder how much energy, bandwidth,HD space is totally wasted on sending everybody spam, junk, messages every day that they will never read. And keeping info for the same. I wonder if it is a reasonably large chunk of the total energy and infrastructure of the whole web?
Maybe we could power a big Chinese city just by getting ourselves deleted from gym mailing lists (weirdly a gym in Cardiff sends me spam mail -- I have never been to Cardiff???).